H40 - GSM/GPRS data logger, level meter

The hydrostatic level sensor TSH22 is most often connected to the data logger H40. The level meter assembly is designed for monitoring the level and temperature of water in wells, reservoirs, tanks and open streams. The measuring set can be delivered in the basic version without data transmissions (datalogger function) or in the version with built-in GSM / GPRS + SMS communication module for data transfer to the database to the server (telemetry station function, GSM / GPRS data Logger).

Due to its dimensions, the GPRS level meter is adapted for measuring levels and temperatures even in narrow boreholes with a diameter of 50 mm
Automatic data transfer to the server via GSM network
Robust stainless steel design with high coverage
High measurement accuracy and long-term stability
Extremely long operating time without battery replacement (up to 20 years for the non-transmission version - data logger, up to 10 years for the telemetry station with GSM / GPRS communication module)
SW support on the server (graphs, tables, exports, ...)
Low purchase price of the level meter
Negligible operating costs for data transmissions at the telemetry station

Basic description

Mechanical design of GPRS level meter H40-TSH22

The level meter consists of an immersion pressure sensor TSH22 and a small data logger H40, from which the pressure sensor is also powered. These are robust devices in stainless steel design with high coverage, which are adapted for continuous operation in a narrow and humid environment of the well. Both devices are connected by a special cable containing a compensating capillary of atmospheric air pressure via a circular connector with IP67 protection. The possibility of disconnecting the devices allows easy eventual recalibration of the level sensor or replacement of one of the parts of the measuring set. The connection connector also contains a special semi-permeable filter, which prevents the penetration of moisture to the probe without preventing the equalization of atmospheric air pressure outside and inside the TSH22 immersion probe.

The GPRS datalogger H40 is mechanically mounted on a stainless steel holder SH1, which also includes a cable suspension of the immersion level sensor. Behind this holder, the entire measuring assembly is usually attached to the wellhead. The design of the holder allows you to place the level meter in boreholes with an inner diameter of only 50 mm. If it is necessary to measure in an even smaller diameter, the datalogger can be removed from the holder. The diameter of the immersion level sensor TSH22 is 22 mm and the hydrologger H40 itself is 40 mm.

Measuring range and length of the connecting cable

The measuring range of the TSH22 level sensor itself is given during its production. Level gauges with a range of 0 to 7 m water column (7 m v.s.) are supplied as standard. Another range from the 5 m and 10 m series can be supplied on request. It is also necessary to state the length of the connecting cable when ordering the set, which is a fixed and non-detachable part of the TSH22 level meter. Any adjustment of the cable length allows only its shortening (for the price of installing a new connector at its end).

For greater level fluctuations than 10 m of water column, level meters type LMP307i / RS485 from BD Sensors s.r.o. can be supplied together with Hydro Logger H40, additionally equipped with a seven-pin connecting connector. These sensors are slightly more expensive than TSH22 sensors, but can be supplied in the 20 m, 40 m, 100 m and 200 m water column ranges.

High measurement accuracy and stability

The measurement and signal processing of the pressure sensor, including complex temperature-compensation calculations, is performed directly in the TSH22 level meter at a virtually constant water temperature in the well. Only the current measured value is transmitted to the connected GPRS datalogger H40 via the connecting cable via the RS-485 serial data communication. This eliminates the possible error of measuring the analog signal, which usually occurs in systems transmitting current or voltage analog signal from the sensor to the measuring part located in the wellhead, where the temperature changes significantly during the year.

The mentioned solution allows to supply this level measuring set even with a measuring error lower than 0.1% of the measuring range. Any recalibration is then performed only on the TSH22 immersion sensor.

Power supply and operating time without battery replacement

The Data Logger H40 has its own 3.6V / 19Ah lithium battery, which, thanks to the extremely low current consumption of the datalogger itself and the connected sensor, allows up to 20 years of operation of the measuring set without battery replacement. Usually, however, the hydrologger is equipped with a GSM / GPRS data module for transmitting the measured data to the server and therefore it is necessary to count on shortening the battery replacement interval at such a telemetry station to 6 to 10 years depending on the frequency and volume of data sent.

Data memory and measurement frequency of Data Logger H40

The Hydrologger H40 contains a large data memory that can hold data for more than 10 years of operation at the usual one-hour measurement interval. This interval is adjustable from 1 minute to 1 day. In addition to the immersion height of the pressure probe and the water temperature, the distance of the level from the wellhead (Status) and the altitude in meters are usually recorded in other recording channels of the datalogger. If the data memory of the data logger becomes full over time, the oldest data will be cyclically overwritten by the newly measured values.

Data Collection

The data stored in the basic set of the level meter without the built-in communication module are transferred for further processing to the notebook by hand via the KP232 / M12 connection cable (the same cable is also used for STELA telemetry stations). The data transfer is performed under the running MOST program, which allows to establish and maintain a database of active stations. In the field, after connecting the laptop to the selected data logger, the program automatically detects the identification number of the device and then adds the newly read data to the newly acquired values stored in the Hydrologger.

The same can be done for telemetry sets of the H40G-TSH22 type with a GSM module, which, in addition to the regular transfer of data to the database to the server, also archive all measured data in their data memory (the datalogger function is preserved).

H40G-TSH22 (Level Meter)

Telemetry set with built-in GSM / GPRS + SMS module - level meter

This is the most common design of a small measuring set. Using the internal GSM module, the measured data are transferred at regular intervals to the database on the server, where they are accessible in the form of graphs and tables to authorized clients via a web browser. Part of data hosting services is also the export of data for a selected period of time or the printing of monthly reports in the form of reports, etc.

In addition to GPRS data transmissions, the Telemetry Station - Hydrologger H40-G can also send preset warning SMS and thus alert the user to a discharged battery, probe failure or exceeding the monitored water level over preset limits.

H40-detail

All parametric settings of the level meter can also be performed remotely via this GSM / GPRS network directly from the Internet via the MOST program (change the recording interval, shift the "zero" measurement, change the frequency of data sessions and many other parameters described in detail in the H40 datalogger manual).

The operating time without replacing the power battery of the Hydrologger H40 depends mainly on the frequency of data sessions to the server. The user-adjustable interval usually ranges from 1 day to 1 week, which corresponds to a period of 8 years to 12 years without battery replacement..

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