Use of Systems for Measuring Groundwater and Surface Water Levels

Dear colleagues!

We are pleased to share with you our experience in using systems for measuring groundwater and surface water levels. Our solution GSM-2 allows not only measuring the level and temperature but also making regular data transmissions via GPRS.

A very important aspect for the operation of devices in Russia is reliable and long-term performance at low temperatures. According to companies that have used the Keller GSM-2 solution, they have never lost data during GSM transmissions at very low temperatures. The temperature at which the GSM-2 operated regularly dropped below -30°C, and the lowest recorded temperature at which the GSM-2 worked was -37°C last winter.

Installation:

• GSM modules are usually installed in 2" well pipes at a height of 0.7…1 m above ground level. At the same time, there is no additional thermal insulation around the GSM module. Of course, when snow covers the ground, the GSM modules are well insulated.
• In several locations known for low temperatures, the GSM module is installed below ground level inside the pipe, with only the external antenna on the cable remaining outside in the open air.

Limitations caused by low temperature:

• The voltage of standard lithium batteries is 3.7 V, but the lithium batteries used by Keller in GSM modules provide 3.9 V. The additional 0.2 V ensures the operation of GSM modules at low temperatures.
• The processor in the GSM module consumes 3.5 V for operation. This allows achieving a better temperature range.

Actual battery life:

• Usually, groundwater level is measured 4 times a day, and data transmission occurs twice a day. With this measurement and transmission frequency, the batteries lasted more than 5 years before being replaced.
• At very low temperatures, I recommend changing the batteries every second year(after two years of use) to be sure that the system will operate during winter at low temperatures.

What drains the battery charge:

• Very low signal level (less than 11 out of 30). If the GSM module does not register on the operator's network (cannot find the network), it makes 3 attempts, using maximum power, then goes into sleep mode and waits for the next data transmission session (according to the program). Then it tries again. Thus, with poor signal quality, the GSM module consumes 3 times more energy than normal. This situation can often be avoided by using a better antenna (for example, a +17 dB directional polarized antenna >3m).
• Taking measurements and recording data does not cause increased battery drain. The process of establishing GPRS/GSM connection requires a large energy consumption.