The above picture shows a SPice 10200 board plugged into an SL99 controller, with all the main features called out.

There are two connectors, one for thermistors and one for conductivity electrodes.

Thermistor connector

The 6-pin connector is for the 3 thermistors. Each thermistor goes between a Gnd (0V) pin and Therm1, Therm2 or Therm3.

Conductivity connector

The 4-pin connector is for the conductivity electrodes. Electrode design is covered later. Each conductivity channel requires two electrodes submersed in the fluid to be detected. One electrode is at circuit Ground (0V) potential, which in the case of a metallic vessel would be the body of the vessel. The other electrode of the pair is referred to as “High”, and would be mounted so the fluid covers it at the fluid level you wish to detect.

Conductivity threshold adjustment

This is a small potentiometer that can be used to adjust the sensitivity of the conductivity switches. Turning this control clockwise will de-sensitize the circuit, i.e. mean a lower resistance (more conduction) is required between the electrodes to trip the detector.

Links LK1, LK2 and LK3

These are used to select the value of feed resistor Vfeed in the thermistor circuits. With the jumper in place, Vfeed is 9.0909K. With the jumper removed, it is 100K. Most applications will have the jumper in place.

Mounting hole

This is referred to later. The picture was taken with the SPice 10200 plugged into an SL99, but without any mounting hardware yet installed.