Specifications

MI 611-211 – October 2005 3. Operation

The message may be enabled, disabled, or cleared. The following Foxboro sensors contain a

preamplifier: 871A-4, 871PH-3, 871PH-4, PH10-.P and ORP10-.P.

ATCSHORT, ATC OPEN

This message reports a problem if the resistance of the temperature compensator is greater or less

than the expected resistance of the device configured. The message for each may be enabled,

disabled, or cleared.

COAT

This message reports an increase in reference junction resistance. This can result from a fouled

reference junction or if the electrode is not immersed in the process solution. The diagnostic

checks the resistance against solution ground. An error message appears if the resistance is greater

than the user set limit. The limit may be set between 0 and 100 kΩ in increments of 10 kΩ. The

default value is 80. The message may be enabled, disabled, or cleared.

NOTE

1. During normal operation, this diagnostic may indicate that the pipe or tank has

gone dry and the sensor is no longer in solution.

2. During sensor maintenance such as cleaning or calibration, this diagnostic may

appear during the times the sensor is out of solution. When the sensor is again

immersed, the diagnostic should turn itself off in a few minutes. If the diagnostic

remains on, then the sensor should be treated as having a coating.

AGING

This message reports an aging glass electrode. An error message appears after a 2-point calibration

in pH buffer solutions when the Nernst slope of the sensor has decreased sequentially five times.

The message may be enabled, disabled, or cleared.

4-20 RNG

This message reports that the measurement that is tied to the analog output is outside the range

that is configured for the application. The message may be enabled, disabled, or cleared.

COMP RNG

This message reports that the measured temperature or the absolute measurement is outside the

temperature or chemical compensation curve that is configured for the application. The message

may be enabled, disabled, or cleared.

MEAS RNG

This message reports that the measurement cannot be displayed accurately in the precision/scale

that is configured for the application. The message may be enabled, disabled, or cleared.

Table 11 shows what diagnostics are available with various Foxboro sensors if enabled and

configured with reasonable limits.