CONDUCTIVITY METER

Typical Number in Hospital:

Cost Bands:

References: 3

The concentration of an electrolyte can be measured from its electrical conductivity. This principle is used to demonstrate the purity of water, and the purity of distilled or de-ionized water is often quoted in terms of its electrical conductivity.

The technique is used extensively in haemodialysis machines to monitor the concentration of the dialysate being fed to the dialyser. Modern haemodialysis machines use a very concentrated electrolyte solution which is mixed with water at the time of use. The concentration delivered to the dialyser is critical for the correct performance of the procedure and can usually be adjusted in a proportionating pump or other mixing device. Conductivity of the mixed dialysate is usually displayed on a meter and an alarm will sound if conductivity is too high or too low. Typical concentration limits are from 130 to 145 mmol/l of sodium.

These devices are incorporated into the haemodialysis machine but the service technician would normally also have a calibrated test instrument through which the dialysate can be passed to verify the performance of the internal monitoring system.