A problem may arise with the generation of residual flow from the Gilson peristaltic pump when the Gilson pump remains switched on but both the PowerLab and STH Controller are switched off (with the STH Controller remaining in "Run" mode). To stop flow from the Gilson peristaltic pump, turn the "Run" switch (on the STH Controller) to the "OFF" position.
EXPLANATION:
The source of the driving voltage is within the Gilson pump. The STH Controller uses the analog voltage connection on the Gilson peristaltic pump to control the pump externally. Normally the analog inputs (of the Gilson pump) have no voltage signal; however, the Gilson pump (when powered on) applies 5 V to the analog input on the rear of the unit. This voltage, combined with the internal resistance within the STH pump (~7 kOhm), is enough to provide a small voltage that is still able to provide flow while the "Run" switch on the STH Controller is enabled.
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