Water Depth and Temperature Instrument - Unidata 8007WDP

This precision battery-powered logging instrument takes long-term unattended readings of water level in bores and wells.

The 8007WDP can measure water depths of up to 50 m and comes in three standard ranges: 10, 20 or 50 metres of water.

It has an overall accuracy of 0.1% of full scale. It records water level, temperature and battery voltage on its internal data logger, allowing long maintenance-free deployments.

Its rugged stainless steel casing, Delrin nose-cone, support cable and 40mm diameter makes it ideal for bore monitoring. It comes with a device to attach the cable to a borehole casing.

The support cable contains a vent tube for barometric compensation and a Kevlar support member for longitudinal stability. 

The 8007WDP measures hydrostatic pressure, from the weight of the water above it. Its internal data logger outputs this as water level. 

The 8007WDP is compatible with Starlog software and has communications ports for connection to a computer or data modem.

If you want to monitor more than just water level and temperature, the 6542B is a good choice. Since the 6542B is a sensor, and can't record data, you'd need a data logger anyway, and could connect additional sensors to it. However, if you only want to monitor water level and temperature, then the 8007WDP, with its internal data logger, may be a good choice. 

Research subject: Instrumentation