Frequently Asked Questions

Our tools cater to a range of soil studies, including ecology, archaeology, wind farms, crop research, agronomy, mineral exploration, and crop diversity.

From Peat Probes to Auger Sets and advanced Window Sampling Systems, we offer a comprehensive selection for various research needs in the renewable energy and low carbon sector.

Our equipment plays a vital role in supporting basic soil research for renewable energy projects, ensuring efficiency in studies related to the development of wind farms and other initiatives in the low carbon sector.

We provide a diverse range, including water level loggers, dip meters, and high-accuracy sensors for water level measurement. Our equipment supports various data collection methods for both manual and telemetry options.

Our rugged and accurate water quality meters are designed for groundwater, surface water, and waste water applications in canals, streams, rivers, wetlands, estuaries, and municipal processing plants. They are ideal for monitoring and maintaining water quality in diverse environments.

Our water quality equipment, including multi-parameter meters and UV/VIS Spectrometers, can be connected to telemetry for powerful monitoring systems. This setup enables event-specific alarms and control relays, allowing for efficient management and automation in applications like sewage treatment plants and water processing facilities.

psia: 30; 50; 100 & 300 this equates approximately to:

Ranges (meters): 10; 25; 60 & 200

Actual cmH2O 10; 24; 59 & 200

For full specifications please see the following link.

22 mm

Officially 0.05% full scale so on a 10m unit that is 5mm. This is both the theoretical but, more importantly, a realistic value. We strongly believe this level of accuracy is not overstated and somewhat contrary to some of the other level loggers available. In short the LevelSCOUT is incredibly accurate for an absolute logger and, we believe therefore that in many cases it is also accurate enough to be used in Surface Water applications.

The battery lasts approximately 4.5 years on a ‘standard’ sampling rate; one reading every 15 minutes. The battery is replaceable.

There are two software suites. Normally, for day-to-day use Aqua4Plus Lite is recommended for its ease of use. When more features are required such as programming for Modbus applications then the full version Aqua4Plus is recommended.

Both versions are available free of charge either by download or by USB memory stick.

UK

• LevelSCOUT: £346
• Titanium: £605
• Comms Unit: £221

Spain

• LevelSCOUT: €445
• Titanium: €780
• Comms Unit: €270

New Zealand

• LevelSCOUT: NZ$ 745
• Titanium: NZ$ 1290
• Comms Unit: NZ$ 475

• Communication Cable to Laptop
• By direct readout cable at the well head
• Telemetry

Stainless Steel or Titanium

Seattle, USA, from the stable of INW renowned worldwide for accurate level and water quality loggers.

50,000

Yes, the LevelSCOUT has replaceable batteries.

One second, other INW loggers are available for sampling times down to one eighth of a second/0.125

Normally 2 years from our date of invoice. For special projects 2 years from the deployment date but proof of deployment date needs to be provided.

This is usual a destructive method and in common with other loggers is not guaranteed to always succeed. This is done by ourselves, in-house in Haslemere.

Yes

Yes

Yes, please specify Titanium

Approximately 160g

Approximately 55g

Yes

No, please specify the special comms unit, £221

This is an entirely new product range but is based on the pedigree of the world renowned INW loggers. Tens of thousands of which are deployed worldwide.

Most popular sizes are kept in UK stock for next day availability. For less common sizes within 2 weeks.

We have number of units available for testing. Availability will need to be discussed with our sales team.

Call +44 (0) 1428 661 660 or email sales@vanwalt.com.

Yes, within the specifications of minimal sampling rates of 1 per second. If a higher frequency is required then we can supply a logger from the INW range which has the minimum frequency of 1 reading each eighth of a second. From our experience for more than 80% of pump test the one second interval suffices.

During the transitional period from Van Walt. Outside of this time from the newly appointed distributor, as yet this is unknown. Or contact Eijkelkamp.

• Warranty? – From the 15th February 2016 any Warranty issues should be directly to www.eijkelkamp.com
• Back-up? – We will continue to provide back-up and support for your existing Diver units.
• Servicing? – We will continue to offer servicing on Diver.
• Performance checking? – We will continue to offer performance checking on Divers and LevelSCOUTs.
• Data retrieval? – We will continue to provide data retrieval.

Our rental fleet is mainly still supplied with Diver but some rental LevelSCOUTs will be introduced.

Yes but the compensation will have to be done manually in Excel.

We do not know but the price of LevelSCOUT is substantially cheaper than Diver and, in fact is fairly close to the price of the Baro Diver.

They were purchased by Novametrix in 2014. The manufacturing company is still based in Delft trading as Van Essen Instruments BV.

Yes, we call it the CT2X, available in Stainless Steel or Titanium. And available as a vented or absolute logger.

Yes, although accuracy is much increased.

Currently ‘No’ but the programmers are preparing cross-platform versions: IOS, Android and Windows (available already)

The software is very intuitive and easy to use but as ever we can provide training. Training by video-conference and in-person. Usually this would not take longer than 10 minutes.

Any time at your convenience.

In test it has shown to be fantastically reliable and robust.

Yes

Yes, with a direct readout cable and standard comms unit.

No

New and Improved software for Seametrics Smart Sensors.

All LevelSCOUT, BaroSCOUT, PT2X and CT2X sensors.

A new streamlined interface, faster drive, automatic sensor detection, improved reporting displays and a real-time graphing function.

• Windows 7, Windows 8, Windows 8.1, Windows 10 or later
• Screen capable of at least 1366 x 768 resolution
• 2 GHz dual core processor with SSE2 support 2 GB RAM (system memory)
• 2 GB of hard-drive space

Yes! When installing 2.0 just make sure to select a new installation directory, anything other than the default \Aqua4Plus in the installer. You can run multiple versions as long as they’re installed in separate directories, much like previous versions of Aqua4Plus.

If you are already using an older version of Aqua4Plus with your USB/RS485 cable there is no need to install a new driver. If you are installing Aqua4Plus 2.0 on a PC that’s never been used with Seametrics Smart Sensors simply make sure you are connected to the internet when you first plug in the USB/RS485 cable and it will automatically install the needed drivers.

Yes! Aqua4Plus 2.0 is compatible with all current PT2X, CT2X, and LevelSCOUT firmware versions, back to August 2015.

Please contact us for firmware options. Many existing units can be upgraded in the field.

Call +44 (0) 1428 661 660 or email sales@vanwalt.com.

Yes! Aqua4Plus 2.0 will be adding the remaining Seametrics Smart Sensor models in the next update.

Aqua4Plus 2.0 has been set up for automatic updates so as long as you have internet access you will always have the latest version ready to go on your PC. It is also available for download on the LevelSCOUT equipment page.

Aqua4Plus 2.0 is brand new. It features an easier to use interface and a new communication driver to allow for automatic sensor detection. It also features a new Reports section to manage and view logged data from within Aqua4Plus and Real-time live graphing.

Please contact Van Walt Ltd on +44 (0) 1428 661 660 or email sales@vanwalt.com.

In the simplest explanation, the user places Snap Sampler bottles into the Snap Samplers, “cocks” the bottles open, deploys the samplers downhole using the trigger cable, and when ready to sample, activates the trigger to seal the water sample in-situ.

The Snap Sampler employs specialty double-opening bottles that collect water in-situ within the well. The Snap Sampler itself provides a mechanical means of holding the Snap bottles open during deployment and a mechanism for triggering the bottles to close only when the user wants to collect the sample.

Snap Sampler bottles have special end caps made of PFA Teflon. The end caps are constructed to attach to a Teflon-coated internal closure spring and to an outer release mechanism. The trigger retracts the release pins, allowing the internal bottle spring to close the end caps. The sampler is retrieved ready for minor preparation and submittal to the lab.

Field testing shows that groundwater sampling with the Snap Sampler is faster and less complicated than pump sampling. No power is needed and no separate devices are needed to determine purge stability, turbidity, or water level fluctuations. Laboratory and field testing of the Snap Sampler show consistent positive results. Blank Snap Sampler bottles are clean and sealed in the same container as an Encoretm soil sampler. Extensive analyte testing by the Army Corps of Engineers and others show the Snap Sampler “passes with flying colors” — with no statistical differences from the control.

The McClellan report by Parsons is one of the more extensive comparisons of passive sampling. While there are some problems with the analysis and broad-brush interpretations, the data sets generated for the Snap Sampler and other methods illustrate graphically how well the Snap Sampler method performed.

Visually it is clear which sampling methods compared best. The Snap Sampler and Low Flow performed very well in the McClellan study. The Hydrasleeve and several others did not perform as well in the McClellan study. Correlation coefficients below 0.50 are generally poor, and several comparisons with the Hydrasleeve (VOC, hexavalent chromium) had low correlation coeffients compared to purge sampling and other passive methods.

The Snap Sampler improves sample collection through simplicity and consistency. Purge methods incorporate several variables the Snap Sampler method does not. These include: exposure to surface air during pouring to sample bottles, pouring technique, rate of bottle filling, weather, potentially different pump depth settings, duration of pumping, purge volume, changes in stability parameter criteria, equipment used, and other site-specific and event-specific variables. These factors combined are illustrated by increased variation of the “traditional purge” results when compared to the Snap Sampler. Concentration trends are discernable much sooner with less variability or “noise” in the sampling data. With data trends discernable sooner, demonstration of remedial effectiveness or monitored natural attenuation (MNA) can be achieved sooner.

Cost savings using the Snap Sampler is commonly 50%. Some sites even exceed that amount. With no waste to dispose (not even extra sample waste), very little preparatory logistics, and simple operation, sampling 20 wells per day should be expected. Improving productivity by 100% or more is the primary driver for cost savings, along with avoidance of waste handling and disposal.

Another driver for cost-savings is reduction in field sampling variability. Reduction of sampling random error from 30% to 10% can make the difference between seeing a trend and not. Demonstrating remedial effectiveness or natural attenuation in many cases is more important from a cost perspective than the sampling itself. All sources of savings should be considered when evaluating overall cost of a groundwater sampling program.

The sample volume of the Snap Sampler VOA vial is slightly less than 40ml. This is not an issue for EPA method 8260 or other standard lab methods for volatiles. For non-volatile analytes that benefit from larger volumes, such as SVOCs, 1,4-Dioxane, explosives, etc., 125ml and 350ml bottles and samplers are available that can increase sample volume for analytes that require more water.

Snap Samplers can be stacked in any combination up to 6, allowing a maximum water volume of 2.1 Liters in 4-inch/100mm and larger wells, and 750ml in 2-inch/50mm wells. Sample volume is a technical limitation, but it is always worthwhile to have a conversation with your laboratory to find out how much water is really required. Advances in technology continually improve analytical performance and often reduce require sample sizes.

No. Snap samples are not restricted to certain analytes. The bottles are open to the well environment during deployment, so no special equilibration is needed beyond restabilization of flow in the aquifer/well. All chemicals/parameters in the water column can be sampled with the Snap Sampler. While no chemical or parameter is excluded from the sample bottles, some analytes require large sample volumes to achieve appropriate detection limits. Sample volume can be a constraint on these analytes or on an extensive analyte list.

In the recommended usage, Snap Samples are collected by deploying the samplers and bottles in advance of sampling. The well re-equilibrates, then you trigger the sampler. Using this method, you need one Snap Sampler for each bottle you plan to collect. The number of samplers you need per sample depends on how much sample volume your laboratory needs. For some analyses such as SVOCs, you may have to combine several bottles to get one analysis.

For simple analysis needs, you may be able to deploy just one Snap Sampler. For longer analyte lists you may have to deploy four or more samplers (and bottles) on one trigger line. There are 40ml glass VOA vials, 125ml and 350 ml plastic bottles available, so combinations of sample bottle sizes usually can accommodate most analyte lists. In 2″ wells the maximum sample volume is 750 ml with 6 bottles set in series. In 4″ wells, the maximum sample volume is 2L with 6 bottles set in series. Our best advice is to consult your lab on their requirements.

Consistency is vital to assure comparability of data from different sampling events. Variability of sampling conditions from event to event can be significant. Wind, temperature, and sampling personnel can each have an effect on sampling consistency, and are not always controllable. The Snap Sampler VOA vial seals under the groundwater surface right in the monitoring well. When retrieved, the sample is already sealed in the bottle that you ship to the laboratory. Since you never transfer sample from a pump discharge line or a bailer into the sample bottle, there is no exposure of the sample to the ambient conditions at the time of sampling. Differences in pouring technique by different field personnel are not a factor. As a result, consistency of sampling method is considerably improved when samples don’t have to be poured.

It’s really not hard at all. Snap Sampler assembly takes just a few seconds. There are four main parts to the sampler, plus screws and the attachment mechanism. The release mechanism (3 of the four parts to the sampler) is held in place with only one screw. Users can become proficient in Snap Sampler assembly with only a few repetitions. Recent improvements include “push-in” trigger cable and single screw connections.

In most applications, the Snap Sampler is dedicated equipment so there is no need for decontamination. The Samplers go right back into th well that they are removed from, limiting the need for cleaning.

If a Snap Sampler needs cleaning, there are just 4 parts to the sampler, plus screws and connectors. Disassembly is relatively easy with very few moving parts. Cleaning can be accomplished by disassembling, rinsing, and brushing with a bottle brush. No special tools are needed beyond those provided with the sampler and normally used for equipment decontamination.

The manual Snap Sampler trigger line is comprised of HDPE tubing with an FEP-coated stainless steel cable. Fluorocarbon (PVDF or PFA Teflon) is also available as tubing material. The tubing attaches to the sampler to the Well Dock. Up to 4 trigger lines can be attached at a 4-inch well head. Up to 2 lines can be attached at a 2-inch well head. The sampler end of the trigger attaches to the release pin mechanism with a press-in ball fitting, similar to a bicycle brake cable. To trigger the sampler, just pull firmly on the trigger cable at the well head. The tubing and sampler stay in place, the cable moves the release pins, the bottles close.

The pneumatic trigger system utilizes a downhole pneumatic actuator that does the trigger pulling for you. You provide bicycle pump air pressure at the surface, which trips the sample bottles to close. Low air pressure is required to activate closure–unlike bladder pumps, there is no need to overcome hydrostatic pressure of submergence to complete sampling. Pressures as low as 15 PSI (1Bar) and normally below 60 PSI (4 Bar) can activate the pneumatic system. A pressure gauge provided in the Pneumatic Tool Kit indicates when the Snap Samplers have tripped.

The Snap Sampler trigger is now available with a downhole pneumatic trigger. With the pneumatic trigger, you can sample from virtually any depth. With a check valve system, the downhole air line fills with water up to the water surface, so you don’t have to overcome submergence pressure to activate the Snap Samplers to close. This makes sampling at depth very easy and reliable. Technically, the activation downhole is hydraulic, but air pressure at surface provides the power to the actuator motion, so we call it a pneumatic system.

In shallow or deep applications, samples are never exposed to air with the pneumatic system. At shallow submergence depths (less than 30ft/10m), air is not released until after the Snap Sampler bottles are closes, and at depth, air is never released downhole. The system has been used to depths greater than 2000 feet /600 meters and there is no theoretical depth limit for the system.

For wells that are difficult to pump because of lift or other limitations, the Snap Sampler is a great way to make sampling deep much easier than the alternatives.

When Snap Sampler bottles are retrieved, the end caps still have the retainer pin tab. This portion of the cap must be clipped off to allow placement of the septa cap. With the clipper tool provided with Snap Sampler, both caps are easily clipped flush with the top of the cap.

To preserve the sample, acid can be added to vial through one of the end caps. Each vial cap has a conical-shaped cavity and a thin membrane for introduction of preservative to the vial. The cavity is sized to accept the proper amount of 1:1 HCl solution to lower the vial pH to <2. To add preservative, one end of the vial should be sealed with a screw septa cap. To the second end, the field or lab technician adds HCl. HCl preservative can be obtained in 1ml ampules or poly dropper bottles from your lab or through a laboratory supply vendor.

Using the back end of the screwdriver tool provided with the samplers, the membrane of the vial cap should be pierced. This allows the HCl preservative to mix with the sample without introducing air to the vial. The cavity should then be topped off with preservative to create a meniscus over the cap cavity. Screw the septa cap onto the vial as usual.

No. For samples that require no dilutions, or where labs have autodilution devices, the Snap Sampler VOA is placed directly in the autosampler just like a normal vial. It doesn’t matter which way is up, either end works just as well. For manual dilutions, the analyst can sample with a syringe directly through the septa and cap membrane; or remove the screw the cap and sample through the cap membrane only; or pull the cap off, hook the end of the spring over the lip of the bottle, and sample from the open container.

The spring inside the Snap Sampler bottles are made of stainless steel with a PFA Teflon- coating. The spring pulls the end caps onto the vial when the Snap Sampler is triggered, and holds the caps in place when the bottle is closed. The green coloring is a primer that allows the PFA to stick to the stainless steel. The PFA itself is clear. The PFA coating is cured at 700 degrees F, so no volatile chemicals remain, and the coating provides an inert barrier between the sample and the stainless steel spring. The spring remains in the sample bottle when submitted to the analytical laboratory. The low-friction PFA Teflon coating on the spring allows autosampler extraction probe to be inserted in the Snap Sampler vials without binding.

Low flow was new at one point. Passive or No-purge methods are alternatives that merit use because many, including the Snap Sampler, have been shown through exhaustive studies to deliver equivalent or more accurate data as low flow purge techniques. In North America passive sampling techniques are accepted by the regulatory community. Peer-reviewed literature, US Department of Defence validation, and standards organisations like ASTM support regulatory acceptance.

Bringing about change is always a slow process. There have been numerous studies done and gradually users and regulators are becoming more familiar with the passive approach for groundwater monitoring. Peer-reviewed literature and 3rd party studies support technical equivalence of results when comparing passive sampling to more traditional groundwater monitoring methods.

Sample volume is a limitation for passive sampling. You can only collect a volume of container(s) that fit into the screen (filter) zone of the well. Narrow diameter wells are more restrictive than larger diameters. Long analyte lists or analytes with large volume requirements can be problematic and may not be possible. However, it is worth discussing the situation with your laboratory. Many labs now have equipment that allows substantial sample volume reduction for analytes like semi-volatile organics. The old requirement for 1 or 2 1-liter amber bottles is falling away as labs update equipment. SVOCs can now be run with 100ml in many cases. Contact your lab to find out what sample volume they really need for your analyte list.

The Snap Sampler requires 2″ (50mm) and larger diameter. Snap Samplers can’t be used in narrower wells.

Snap Sampling is best used for longer-term monitoring with extended periods between sampling events. For some analytes, a pre-deployment period is required for plastic components to equilibrate downhole (VOCs, other organic compounds). For inorganic compounds, it is possible to collect samples after short deployment periods, but the user should consider sampling objectives and the sampling environment before choosing this approach. The Snap Sampler could be better than a bottom-filling bailer for repeated sampling, but the user needs to understand the limitations of the method. Pouring sample into lab containers, for example, could alleviate concern for organic sorption when sampling organics in short deployments.

For one-time sampling, the Snap Sampler may not be the most cost-effective approach, unless the well is not appropriate to purge e.g. low- yielding. The cost of initial installation of equipment can be high for a one-off sample event, however relatively inexpensive in comparison to installing a new well. For very deep wells this may however be a best fit option, even for a single event.

Pair-wise statistical comparisons are the best approach. Student’s t-Test, Wilcoxon Sign Ranks test and other parametric and non-parametric tests can be used at the user’s discretion. X-y plots with regression statistics on log-log scales are useful for visualizing data. Historical comparisons are also useful for visualizing ranges of previous data to current sampling results. Comparison samples should be collected as close in time as feasible. This usually means that Snap Samplers are deployed in advance of sampling (1-2 weeks or more). Snap Samples are “snapped” closed, then comparative samples are collected immediately after. This can be done with adjacently deployed peristaltic tubing or pump(s), or after removing Snap Samplers and deploying the pumping device.

The more comparison results you have, the more likely it is there will be an appropriate statistical comparison. Any individual result is subjectto variability associated with many unknowns, including contaminant stratification, contaminant redistribution due to pumping, pumpingwater from beyond the screen zone, geochemical change in the well bore itself. Each of these factors is well-specific. On average, Snap Sampleresults mimic low flow results. However, there will be a mix of higher and lower concentrations results. Most will be close, but some will besubstantially different. As long as these differences “average out” then you can consider a comparison equivalent. If there are strong biases,you should look at sample size at a possible culprit. Other well-specific or site specific considerations could also be at play. We don’t knowperfectly what the “right” result is when comparing two methods. If the Snap Sampler has slightly higher results, it might be due to the fact thatVOC samples are not exposed, for example, or metals samples are slightly higher for purge samples due to higher turbidity.

This can be true for “active-no-purge” samplers but is much less likely for true passive devices such as the Snap Sampler.

Some of the latest research papers are suggesting that the sampling method has little importance to the analytical results. In fact, one of these papers suggests that the choice of sampler should be based on other considerations: “Monitoring well sampling methods should be selected based on factors such as cost and ease of implementation rather than concerns regarding data quality.” (By the ESTCP on Methods for Minimisation & Management of Variability in Long-term Groundwater Monitoring Results)

Most labs are now setup so they can analyse smaller samples but a discussion may need to take place between you and your lab to confirm this. The Snap Sampler can duplicate a sample by stacking sample containers. There are various options to accommodate a range of volume requirements.

Other sampling methods are still used, in particular devices such as peristaltic and bladder pumps. Nonetheless, there are some applications when passive sampling might be more convenient: deep or low recharge wells, infrequent but repetitive sampling in remote areas.

We understand that consultancies are restricted by regulators, however we believe that this technique is more suitable for some wells i.e. slow recharge, low-yielding etc. A negotiation with the regulator may need to take place, to suggest a more appropriate technique for your circumstances.

The Snap Sampler is made to your well’s depth specification when you order it. If you are required to change the depth, the length of the tubing will need to be adjusted. In a shallower well using the manual trigger, a new trigger line is usually required because of fixed fittings on both ends of the trigger. For deeper pneumatic triggering systems, the tubing can simply be cut to shorten a depth, or a splice can be added with tube fittings, accruing minimal costs.

Snap Samplers are normally dedicated to individual wells and used there for long periods of time. This is the most cost-effective way to avoid difficulties of decontamination and risk of cross-contamination. However, if Snap Samplers need to be moved from one well to another, they can be decontaminated using standard decontamination procedures and cleaning with a suitable decontaminant like Deconex. Blank testing can be employed to assure cleanliness prior to reuse.

Cost of the Snap Sampler bottle-ware is offset by the savings achieved through much quicker sampling, avoidance of purge water handling and disposal, and equipment rentals. The high quality components of the bottles necessitates a relatively high cost, but assures high quality as well. The vials are sealed in VOC-impermeable, foil packaging. This allows for long-term storage without risk of contamination and will remain sterile until the packaging is opened. Each VOA vial/bottle contains a Teflon coated spring which is needed to snap shut the lid of the sampler. Sealed samples allow collection of unexposed samples, assuring very high quality.

The Snap Sampler is easy to use. A demonstration video is available via YouTube. Additionally our staff can walk you through instructions.

As a rule, YSI recommends that a calibration be performed or verified daily, before sampling starts. But in general, calibration frequency is determined by the user and the importance of the data. The more critical the data, i.e. when used for compliance purposes, the more attention that should be paid to timely calibrations.

The calibration of newer optical based dissolved oxygen meters is very stable but YSI still recommends that it be verified on a regular basis to ensure accurate data.

Your data is as good as your calibration.

Place the sensor in its calibration environment and check to see that the instrument is reading the calibration value for the current barometric pressure. For example, if your ‘true’ barometric pressure is 750, divide this number by 760 and then multiple by 100% to calculate what your instrument should be reading in water-saturated air or air-saturated water.

750/760 x 100 = 98%

A post-check can also be performed with this value in mind. If, for instance, you calibrate your instrument to 98% and then conduct your DO testing, you can place the sensor back into the same calibration environment and it should read +/- 2% (+/- 1% on optical) of 98% once stable.

DO instruments need to be calibrated to “True” barometric pressure, i.e. a barometric pressure value that has not been corrected to sea level. Laboratory barometer readings are usually “true” (uncorrected) values of air pressure and can be used “as is” for DO calibration. Weather service readings are usually not “true”, i.e., they are corrected to sea level, and therefore cannot be used until they are “uncorrected”. An approximate formula for this “uncorrection” is:

True BP = [Corrected BP] – [2.5 * (Local Altitude in ft. above sea level/100)]

There is no need to recalibrate new digital or older analog models when the instrument is turned back on. Instruments are designed to record and save the calibration values so no recalibration is required at power-up unless it requires normal calibration as mentioned in #1.

You can also “verify” that the instrument is holding it’s calibration by knowing the original calibration value (98% as an example) and the instrument should read within +/-2% (+/- 1% on optical) of 98% upon power on once it’s stable.

There really is no set time period. Regardless of the sensor type that is used, wait for the temperature and dissolved oxygen values to become stable. For dissolved oxygen systems that use a polarographic sensor, achieving stability takes about 5-15 minutes. For galvanic and optical sensors, the readings will reach stability almost immediately after turning on unless the ambient temperature has changed. For each sensor type, it is recommended to make sure there are no water droplets on the sensing element (membrane) to help ensure quicker stability and ensure calibration accuracy.

For the best calibration results, it is very important to have the DO system in an environment where the temperature is stable and does not change prior to, or during the calibration procedure.

No. Dissolved oxygen sensors are calibrated to and measure the partial pressure of oxygen. Therefore, after performing an accurate calibration, the sensor will automatically compensate for changes in pressure. For systems that are using the DO% Local function, the calibration value will be 100% regardless of the altitude or barometric pressure and the internal barometer will be used to keep the saturated value at 100%.

When increasing the amount of stirring does not result in an increase in the dissolved oxygen readings, enough stirring is being supplied.

As a general rule, YSI recommends that the membrane be changed every 2-8 weeks. This is dependent on the sampling application. Additionally, keeping the membrane clean and in a moist environment between uses will lengthen the membrane life.

When measuring samples with high levels of hydrogen sulfide, a weekly membrane change will reduce sensor cleaning and maintenance and thus provide better performance. When measuring in clean water, membrane changes can easily go beyond 4 weeks without negative effects.

Maintaining electrochemical sensors is relatively easy but is only necessary when the sensor no longer performs to factory established specifications.

When calibrating, YSI instruments perform a sensor performance check. If the sensor is outside of its normal working parameters, the instrument will give an out of range indication. Before cleaning electrodes, always try fresh probe electrolyte solution and a new membrane.

It is normal for a polarographic sensor’s silver anode to darken over time due to the build up of silver chloride. This typical darkening will not affect the sensors performance so do not clean the electrodes just because they ‘look dirty’. Long term exposure to hydrogen sulfide can cause darkening of the anode that will influence a sensors performance. Typical symptoms will be jumpy readings, inability to calibrate and/or low probe current, both of which may respond well to cleaning. Typically, the electrodes will require cleaning or servicing about once per year.

Go to the troubleshooting and maintenance section of the instruments instruction manual (Professional Plus or ProODO ® onboard “Help”) for the best advice regarding resolving these issues.

The optical sensing elements are warranted for 1 year but may last longer. Be sure to keep the sensing element clean and stored in a moist environment between uses to obtain the longest usable life possible.

Each groundwater sampling technique characterizes contamination in the groundwater differently. It is important to understand the conceptual basis of any sampling technology since results from each method may differ. These differences should be considered when comparing sampling methods for interpreting sampling results. Differences may occur when comparing 3-volume purge, low-flow or passive sampling techniques. These differences do not necessarily indicate inaccuracies, but reflect the nature of the sampling methods.

When comparing passive groundwater data to data collected with other types of sampling devices, even other types of passive sampling devices, the team has found that the more variables that are introduced into your sampling technique then there is reduced data reliability. When compared to passive sampling methods, traditional groundwater sampling methods introduce more variables such as where your groundwater sample is being collected (i.e., biased toward zone of highest hydraulic conductivity), increased turbidity concern since increase disturbance to the well, and possible unusable data due to cross contamination from well to well. Passive sampling methods require minimal handling procedures and equipment needs; therefore, reduce these errors.

When performing ongoing sampling events, it is critical to place the passive sampler in the same location or depth for consistency and comparability of results over time. Sampling at a consistent deployment depth can improve data reproducibility. The Team expects high reliability or reproducibility of groundwater data if for each sampling event you are collecting groundwater with the same device at the same interval using the same sampling methodology. At this time, the Team has not designated a “margin of error” associated with reproducibility. In general, the Team agrees that in a well that has a low temporal variability, a 1:1 correlation is expected if using the same sampling device with the same methodology.

The Team has had no reports of any negative effect of high or low groundwater pHs on Polyethylene Diffusion Bags (PDBs), Rigid Porous Polyethylene (RPPs) samplers, or Regenerated Cellulose Dialysis Membrane (Dialysis) samplers (i.e., diffusion-type sampling devices). Polyethylene materials in general are resistant to attack by both acidic and basic solutions. PDBs, RPP samplers and Dialysis samplers have been used to successfully sample ground waters and acidified laboratory test solutions with pHs ranging from 2 to 11 after equilibration periods of up to 4 weeks without any compromise of sampler integrity.

The SNAP Sampler™ spring is PFA (i.e., Teflon) coated stainless steel. There has not been detectable degradation of the spring material due to preservation. For VOA samples, the sample is preserved with the spring left in the glass vial unopened. For metal sampling, it is recommended to remove the spring prior to preservation, which is very easy to perform. Air exposure of a metal sample once collected is not important in a Snap Sample because any precipitation reactions due to exposure will be redissolved during the preservation process.

Our system, built on over 40 years of equipment and site expertise, is highly versatile and robust. It uniquely supports a range of sensors, manufacturers, and parameters, providing solutions for both single monitoring points and complex, integrated multi-parameter installations.

We offer comprehensive support, helping you plan your telemetry requirements. This includes suggesting suitable sensor solutions, providing cost-effective datalogger options, and assisting with site installation. Our support extends throughout the duration of your project.

Absolutely. Our telemetry system is designed for flexibility. Whether it’s a single monitoring point or a multi-point installation, we tailor solutions to meet your specific requirements, ensuring secure and efficient data collection across diverse sensors and parameters.

A wireless telemetry system that turns any pulse, Modbus or SDI-12 sensors into a wireless unit. Communicating the data over a considerable distance (up to 10km line of site) via radio frequencies.

Designed and developed in-house by the Van Walt team. Manufactured in the UK.

Any sensor that speaks the same language as the vanwaltDataSlave, that means Modbus; SDI-12; or Pulse connection.

This depends on the communicating protocol used by the sensors but multiple sensors may be attached. Please contact us to discuss.

10km line of site

There is no limit to the type of parameter you can measure with the DataSlave. As long as your sensor talks the languages of the unit (Modbus; SDI-12; Pulse or a Cabled connection), then the DataSlave will be able to communicate with it. Please contact us to discuss.

Use your PC via the radio readout option or remotely via our vanwaltDataHub, via radio to the telemetry system.

With your sensor software on your laptop or as a .csv file using the internal logger. If you use our DataHub data can be read and managed via the vanwaltCONNECT interface.

As often as you want/need. The more frequently the data is transferred the more wear on the batteries in the unit.

With 15-minute data collections and hourly uploads the battery will last up to 18 months when connected via the vanwaltDataHub system.

The preferred and tested telemetry option is the vanwaltDataHub.

The data is stored either in your sensor or in the DataSlave. Once it is exported, if using the vanwaltDataHub it is stored in Rackspace, one of the world’s leading cloud internet storage providers.

Yes, the DataSlave is enclosed inside a fully water proof, IP rated, heavy duty aluminum enclosure which can be mounted on a wall, post or surface.

Yes, when connected to a vanwaltDataHub and managed via our vanwaltCONNECT software.

To change the settings, you need to be within radio distance. So, it is possible to change the settings for units deployed in difficult to access locations as long as you were within radio line of site.

The main body of the enclosure is 8 cm x 12 cm x 12 cm, the Antenna protrudes a further 8 cm.

We offer the vanwaltDataHub under a Logger for Life scheme and also as a ‘Keep-On Going’ Service Level Agreement.

We would always recommend a site survey before deploying a vanwaltDataSlave , particularly if connecting several units together and relying on telemetry to receive the data. For more simple applications then the only question to ask is: “how far is your line of sight in order is to retrieve your data?” A site survey will ensure more complicated applications are viable such as urban or obstructions to the line of site.

The vanwaltDataSlave is offered as a stand-alone unit, OEM unit or as part of a telemetry network, to purchase or via our Logger for Life scheme.

Keep It Simple Sensing

A true “plug and play” environmental telemetry system to monitor water level and temperature. Data collected every 15 minutes from a deployed system on site transmits data for download, directly to your phone, PC, or laptop once a day. An email will be sent to you each day as soon as a new data set is available.

A lot of technology has gone into the development of this system to make it very simple for our customers to use. vanwaltKISS makes collecting groundwater level and temperature data very simple in several ways:

• Connecting the sensor cable and vanwaltKISS unit powers the device on
• Wait for it to go through a colour display sequence (power and connection process test and confirmations)
• Feed the sensor down the well
• Bespoke, self-levelling design for easy deployment in wells from 1 inch
• Standard data recording every 15 minutes, sent every 24 hours (08:00 UTC)
• No need for a BaroSCOUT/barometric data – compensated pressure above the sensor provided
• View and download the data via the vanwaltCONNECT-LITE web-browser based dashboard
• Use downloaded data as required
• Reduced costs with no additional charges because system includes:
  • 2-year roaming sim
  • 2-year warranty
  • 2-year battery life
  • Storage for 2 years’ data
  • After 2-years, fully serviced and restart all of the above for another 2-years with a further extension on the warranty
• Standard, high-accuracy sensor
• Standard cable length of 30 m (can be reduced in length to fit wells. A 50 m length cable is available at an extra cost).
• True “plug & play” solution, providing unparalleled simplicity of deployment, so no 3rd party installation required (available if requested, and even then minimal time and resources required to keep costs down).
• Data security using the https:// protocol.

• Designed from scratch by Van Walt Ltd
• Made in the UK to our specifications
• Owned, sold and distributed by Van Walt Ltd

Example applications include:

• Environmental research
• Groundwater monitoring projects & site assessments
• Tidal studies
• Groundwater monitoring network automation
• Watershed, drainage basin and recharge areas
• Stream gauging, lake levels and reservoirs
• Wetlands & Water Meadow monitoring
• Storm water run-off monitoring
• Environmental monitoring
• Aquifer level monitoring
• Aquifer storage & recovery
• Flood risk monitoring
• Wetland and Peat Bog monitoring & surveys
• Final outflow monitoring for groundwater remediation projects

The Keller PR26 vented sensor, measuring depth and temperature. A Keller vented sensor to add EC to temperature and depth is available as an option.

A Keller CTD can be added to monitor conductivity.

Standard length is 30 m. This can be cut down to length when needed. Alternatively, a 50 m cable is available as an option (chargeable).

From 1 inch diameter upwards

Includes a bespoke lithium battery with integrated super capacitor with a minimum life of 24 months (replaced during 2-year re-commissioning service)

The vanwaltKISS is a low energy device.

• Service vanwaltKISS unit
• Replace battery
• Reactivate SIM
• Verify sensor
• Re-issue 2-year warranty

There is no annual/bi-annual subscription charge as the Sim card and airtime is included in the sale/rental price.

vanwaltKISS is available to purchase and also for long term rental for periods of one month or longer.

Call +44 (0) 1428 661 660 or email sales@vanwalt.com.

• Bespoke auto-centering design to IP68
• 88 mm diameter
• 170mm Height to seat at the 1″ well (height reduces as well diameter increases)
• 1.3 kg (without sensor)
• Powder coated stainless steel 304

vanwaltKISS has a security eyelet built into the unit which can be used to secure/padlock a unit on site. Alternatively, the unit can be positioned inside a well cover – see photograph

[PHOTO HERE]

We recommend a plastic, fibreglass or thin metal well cap to maximise the signal strength to the unit. The diagrams below outline the dimensions required to site vanwaltKISS securely inside the well, including placing 2 units side by side.

[PHOTO HERE]

vanwaltKISS uses a roaming 2G/4G roaming SIM

A powerful, flexible system of electronics, conveniently packaged in a heavy-duty enclosure which performs as a hub to collect and store data securely from deployed environmental and other sensors. The datalogger is capable of simultaneously connecting to sensors even if they use different protocols.

Designed and developed in-house by the Van Walt team. Manufactured in the UK.

The vanwaltDataHub can connect to many different sensors, for example, ModBus; SDI 12; Pulse; Relays; Analog and Digital.

As standard the DataHub is supplied with 6 connector glands, however by using a “splitter”/junction box several hundred sensors could be connected to each vanwaltDataHub.

Some examples are: Water Level; Water Flow; Water Quality (conductivity, pH, ORP, DO, Turbidity, Temperature and more); Floating Hydrocarbons; Soil Moisture; Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) data, atmospheric and weather parameters and many more.

Data can be collected from the DataHub manually using an industrial SD card or via GPRS (2G, 3G or 4G); Radio or Satellite.

Data files are in a .csv format for easy import into a spreadsheet.

1. Data can be uploaded directly from the logger to the vanwaltCONNECT* server which makes it viewable on your desktop.
2. Data can be forwarded directly from the logger to your own server by FTP.
3. Data can be downloaded to your laptop from the logger through a cabled usb connection.

* vanwaltCONNECT is the remote interface for the vanwaltDataHub. Data collected by the DataHub can be accessed from your desktop or mobile and shared between users to whom permission is given.

You can set this to match your requirements. Sampling frequency is however dependent on the sensor. In some cases this could be as frequently as several times per second. In most cases this will be from just a few seconds, to hours or days.

In principle, if you have sufficient power and signal, data can be uploaded as often as you require it. In practical terms, mostly this means from every 30 minutes to hourly or daily uploads.

This will depend on many factors including the sensor type, the quantity of sensors on the system, data collection intervals, data upload frequency, signal strength. Battery size, type and solar array options should be discussed prior to installation so they are matched to the requirements.

Collected data are stored on non-volatile memory. The internal memory is backed up to an internal micro-sd card. Data forwarded to our server are stored, backed-up and maintained by Rackspace, the number one managed cloud company.

The electronics of the vanwaltDataHub are enclosed inside a fully water proof, IP rated, heavy duty aluminium enclosure which can be mounted on a wall, post or surface.

Yes, using the vanwaltCONNECT interface you can set up alarms.

No, using the vanwaltCONNECT interface you amend and adjust sensor settings, data collection intervals and upload times.

The enclosure is 260 mm long; 120 mm high and 160 mm wide. Weight including the batteries is 6.6 kg.

We offer the vanwaltDataHub under a Logger for Life scheme and also as a ‘Keep-On Going’ Service Level Agreement.

As a stand-alone data logger the vanwaltDataHub will work in any location. In addition, and unlike some other telemetry systems, the vanwaltDataHub is not solely reliant on a mobile phone signal as you can use our radio or optional satellite alternatives. The options should be discussed prior to installation so they are matched to the requirements.

Customers are billed for all charges incurred during the rental period upon returning the item. Payment terms are 30 days from the invoice date. Consumables ordered with rentals are billed upon sending.

Any attempt to repair rental equipment without Van Walt’s consent is prohibited. Costs resulting from damage, negligence, or situations unrelated to normal wear and tear will be charged to the customer, in addition to rental charges.

Equipment must be properly maintained throughout the rental period and returned in the same functional condition. Failure to do so may result in a fee of GBP100 per hour. Customers should notify Van Walt within 24 hours of receiving equipment regarding any issues, and check for shortages upon receipt. The minimum rental period is one week, and additional days carry a 20% charge.