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Hello,
I am trying to confirm the correct wiring of a Honeywell pHG-1 / Meridian III glass pH sensor to a Honeywell APT4000PH analyzer.
The pHG-1 sensor has:
Glass pH measuring electrode
Reference electrode
Temperature compensation element
A metallic Pt disc at the sensor tip
A Blue wire that has electrical continuity to the Pt disc
My main question is:
Is this Pt disc / Blue wire the solution ground (ground rod / auxiliary electrode), rather than a cable shield or protective earth?
The APT4000PH has terminals associated with the reference electrode, auxiliary/solution-ground electrode, and a separate terminal marked “C” for shield.
The existing installation has terminals 2 and 3 jumpered.
I would like to confirm whether the correct arrangement for a pHG-1 equipped with the Pt disc is:
1. Reference electrode → terminal 2
2. Blue wire / Pt disc → terminal 3 (auxiliary / solution ground)
3. Remove the jumper between terminals 2 and 3
4. Cable shield only → terminal C
Or should the Blue/Pt-disc conductor be connected somewhere else?
I am particularly concerned about connecting the Pt disc to terminal C, because if the Pt disc is a true solution-ground electrode, that could incorrectly connect the process liquid to the cable shield/earth system and potentially introduce ground-loop current into the pH measurement.
I would also appreciate confirmation on two related APT4000 settings:
Should SensoCheck be enabled when the sensor has a dedicated solution-ground electrode?
Should the APT4000 sensor connection/configuration be set to symmetric for this type of sensor?
If anyone has actually used a Honeywell pHG-1 / Meridian III sensor with an APT4000PH, or has documentation identifying the function of the pHG-1 Blue wire / Pt disc, I would greatly appreciate your experience.
I can also provide the pHG-1 wiring diagram and APT4000 terminal diagram if needed.
Thank you.
I am trying to confirm the correct wiring of a Honeywell pHG-1 / Meridian III glass pH sensor to a Honeywell APT4000PH analyzer.
The pHG-1 sensor has:
Glass pH measuring electrode
Reference electrode
Temperature compensation element
A metallic Pt disc at the sensor tip
A Blue wire that has electrical continuity to the Pt disc
My main question is:
Is this Pt disc / Blue wire the solution ground (ground rod / auxiliary electrode), rather than a cable shield or protective earth?
The APT4000PH has terminals associated with the reference electrode, auxiliary/solution-ground electrode, and a separate terminal marked “C” for shield.
The existing installation has terminals 2 and 3 jumpered.
I would like to confirm whether the correct arrangement for a pHG-1 equipped with the Pt disc is:
1. Reference electrode → terminal 2
2. Blue wire / Pt disc → terminal 3 (auxiliary / solution ground)
3. Remove the jumper between terminals 2 and 3
4. Cable shield only → terminal C
Or should the Blue/Pt-disc conductor be connected somewhere else?
I am particularly concerned about connecting the Pt disc to terminal C, because if the Pt disc is a true solution-ground electrode, that could incorrectly connect the process liquid to the cable shield/earth system and potentially introduce ground-loop current into the pH measurement.
I would also appreciate confirmation on two related APT4000 settings:
Should SensoCheck be enabled when the sensor has a dedicated solution-ground electrode?
Should the APT4000 sensor connection/configuration be set to symmetric for this type of sensor?
If anyone has actually used a Honeywell pHG-1 / Meridian III sensor with an APT4000PH, or has documentation identifying the function of the pHG-1 Blue wire / Pt disc, I would greatly appreciate your experience.
I can also provide the pHG-1 wiring diagram and APT4000 terminal diagram if needed.
Thank you.
