Herpstat 4 LCD goes blank.

Issue: Herpstat 4 LCD shows as blank screen.


What triggers it:

This is first triggered by an issue with a probe that is causing the safety relay to trigger.  This could be due to one of the following:

One of the probes is either damaged or has water penetration into the sensor and is causing an invalid error.

The probe wires are running alongside of the 120V electrical cords and its getting electrical interference causing an invalid error.

The high / low alarms are enabled and the safety relay is set to trigger on the alarms and the temperature range was breached.


What causes the lcd to go blank:

This issue has been identified as a unusual combination between a batch of certain relays in combination with certain lcd screens.  The components are fully functional but interact with each other causing the lcd to go blank.  Identical units produced at the same time may not have the issue. The screen goes blank when the safety relay is triggered due to invalid probe reading.


What is affected:

During an invalid error on a probe the relay is triggered for safety which cuts power to all four outputs and the unit starts to beep.  There will be no heating while beeping and still in error condition.  If the error is corrected the unit will return to normal operation and stop beeping.    However, once the beeping stops and the unit returns to normal operation you will not see the data on the screen until power is cycled on the unit.


Ways to prevent this:

Check your probe wires and separate them from 120V electrical cords by 6 inches or more wherever possible to prevent electrical interference.

If you have a probe being used in a high humidity environment then consider upgrading it for a steel tipped probe.

If you have a device exhibiting this symptom the firmware can be upgraded to fix the problem.  First check which firmware your device has by unplugging it and plugging it back in.  The startup screen will display your current firmware.  Firmware 4.3 and above have the solution built in.   To have your firmware updated send the unit into us for service using the following information:


Herpstat Repair Request


There is no charge for this service and it will be handled under our normal warranty terms


The firmware update only solves the lcd going blank due to the error condition.  This would then give you the ability to see which probe is causing the problem.  We will include one replacement probe when the unit is returned at no charge.   

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