Conductivity Controller in a Machine Washer

Question:
How does a conductivity controller regulate a dosing pump in a machine washer?

Answer:
A conductivity probe would need to be set up in the sump of a machine washer. The conductivity recorded is sent to the conductivity controller that regulates the pump (usually a peristaltic pump) that dispenses the detergent into the sump. The pump dispenses until the correct conductivity is reached for the desired concentration. Typically a concentration of 0.5% or 0.1% detergent is desired. For example, for a 0.5% Solujet concentration, enough detergent concentrate is pumped into solution until the sump reaches 2.45 mS at 22 deg C (Alconox, Inc has conductivity VS concentration curves available for each brand at 22 deg C). Once the correct concentration has been reached, the wash cycle starts.

Since conductivity is temperature dependent if hot water is used a new conductivity curve must be generated that reflects the higher temperature. If the customer provides the Alconox Technical Team the higher working temperature then a curve could be generated. Alternately, if the customer has access to a conductivity meter they could simply generate the appropriate curve for their working temperature.