The DrDAQ can indeed be used for conductivity measurements by using the 3 available EXT. channels as data acquisition in Picolog, plus the Resistance channel as an overall check.
EXT. 1 CHANNEL logs sample temperature measured with an LM35, or other miniature sensor.
EXT. 2 CHANNEL logs voltage.
EXT. 3 CHANNEL logs current value coming from a standard current probe (Pico) or high precision commercial Hall Effect sensor.
RESISTANCE CHANNEL logs resistance independently, as an overall control, within the limitations described below.
A fixed voltage (AC or DC, depending on material and status, liquid, solid, jelly, etc. to be measured) is applied to the sample and current flows. This power will increase the temperature of the sample. The DrDAQ will record all 4 quantities in PICOLOG. Resistance at any different temperature is calculated by the PICOLOG's math channel by Ohm's law. Then the standard Conductivity equation, knowing area and length, is used in another math channel to calculate Conductivity. Picolog will then automatically graph Conductivity Vs. Temperature. In between the applied voltage is switched off at various temperatures and the resistance channel, connected via a switch, records raw resistance at any desired temperature as an overall check. This resistance can then be converted to conductivity by applying the standard equation and this result used for comparison. Due to the lower limit of the Resistance channel (1 KOhm) this channel could not be used depending on the measurement range needed. Therefore an automated electrical conductivity measurement system is possible within the DrDAQ/PICOLOG capabilities.
In synthesis you need:
- DrDAQ + PICOLOG software.
- Suitable AC Variac or adjustable DC Supply.
- Standard current probe/current sensor.
- LM35 type temperature probe or any other miniature probe.
- Special fixtures for the application of current flow/temperature measurement. This depends on what kind of material the measurement has to be taken.
This method and the DrDAQ would be especially useful if you needed to collect data as control in a continous process: the DrDAQ would record and display Conductivity and Temperature for an undefinite time period.