Instruction manual
91
MODEL Xmt-P SECTION 10.0
TROUBLESHOOTING
10.2.8 pH mV Too High
This message means the raw millivolt signal from the sensor is outside the range -2100 to 2100 mV.
1. Verify all wiring connections, including connections in a junction box.
2. Check that the pH sensor is completely submerged in the process liquid.
3. Check the pH sensor for cleanliness. If the sensor look fouled of dirty, clean it. Refer to the sensor instruction
manual for cleaning procedures.
10.2.9 No pH Soln GND
In the transmitter, the solution ground (Soln GND) terminal is connected to instrument common. Normally, unless
the pH sensor has a solution ground, the reference terminal must be jumpered to the solution ground terminal.
HOWEVER, WHEN THE pH SENSOR IS USED WITH A FREE CHLORINE SENSOR THIS CONNECTION IS
NEVER MADE.
10.2.10 Sense Line Open
Most Rosemount Analytical sensors use a Pt100 or Pt1000 RTD in a three-wire configuration (see Figure 10-3).
The in and return leads connect the RTD to the measuring circuit in the transmitter. A third wire, called the sense
line, is connected to the return lead. The sense line allows the transmitter to correct for the resistance of the in and
return leads and to correct for changes in lead wire resistance with changes in ambient temperature.
1. Verify that all wiring connections are secure, including connections in a junction box.
2. Disconnect the RTD SENSE and RTD RETURN wires. Measure the resistance between the leads. It should
be less than 5Ω.
3. The transmitter can be operated with the sense line open. The measurement will be less accurate because
the transmitter can no longer compensate for lead wire resistance. However, if the sensor is to be used at
approximately constant ambient temperature, the lead wire resistance error can be eliminated by calibrating
the sensor at the measurement temperature. Errors caused by changes in ambient temperature cannot be
eliminated. To make the warning message disappear, connect the RTD SENSE and RETURN terminals with
a jumper.
10.2.11 Need Factory Cal
This warning message means the transmitter requires factory calibration. Call the factory for assistance.
10.2.12 Ground >10% Off
This warning message means there is a problem with the analog circuitry. Call the factory for assistance.