AMMONIA User Manual
AMMONIA_User 9/09
3
8
2.6 Sensor Diagnostics
Offset Adjust
is the value required to make the displayed
pH, NH3, or temperature match your last calibration.
Default Offset
is the
Offset
after a
Factory Reset
.
pH & NH3 sensors with offsets twice the default offset will
not usually track & have failed, contaminated or fouled.
Refer to Section
4.2 Calibrate Faults.
Measured Level
is the sensor voltage
measured by the Analyzer.
Useful when converting 4-20mA currents
& diagnosing non-tracking sensors.
The Analyzer uses the
card ID
to
auto-configure on new driver cards.
Some cards also use this level to determine range.
Offset Adjust
-35.0000
Default Offset
-35.0000
Measured Level
164.0 mV
Input card ID
74.6 mV
Diagnostic cont.
Sidebar:
Gain & Default Gain
When you calibrate an ammonia sensor, the Analyzer adjusts the GAIN to make your measured
value match the displayed value.
Offset & Default Offset
When you calibrate a pH, ammonia, or temperature sensor, the Analyzer adjusts the OFFSET to
make your measured value match the displayed value.
When you two point calibrate a 4-20mA input, the Analyzer adjusts both OFFSET and GAIN.
Manual Sensors:
These sensor types use only the OFFSET to set the displayed value.
The Analyzer ignores GAIN for these sensor types.
For example when you
Calibrate
a sensor to
display 48.5 degrees,
Offset Adjust
will display 48.5.
Measured Level:
pH sensors have a well defined mV to pH relationship.
Example pH7 = 0mV, pH10=176 mV and pH4 = -176 mV.
Displayed sensor value = (
GAIN
x
Measured Level
) +
OFFSET
.
Using this simple equation, you can directly modify the OFFSET & GAIN to get a desired display.
This is seldom done, but it’s convenient for some unusual sensor types.