Basic Setup; Sensor Error Adjustment (Dtm Adjustment Function); D/A Analog Output Adjustment (4 And 20 Ma Trim) - ABB TTF200 Operating Instruction

TTF200 FIELD-MOUNT TEMPERATURE TRANSMITTER | OI/TTF200-EN REV. A
7.5

Basic Setup

7.5.1 Sensor error adjustment (DTM Adjustment
function)
Sensor error adjustment can be performed in the DTM by
navigating to the menu path "Device / Maintenance /
Adjustment / Trim low or Trim high".
For sensor error adjustment, the sensor connected to the
transmitter must be brought to the lower range limit value
temperature / Trim low using a water quench or oven. It is
important to make sure the temperature is balanced and
stable.
In the DTM, check that the proper adjustment temperature
has been entered for the sensor before adjusting it. Based
on the comparison of the adjustment temperature entered
(setpoints) with the digital temperature measured by the
transmitter, which is available after linearization in the form
of HART temperature information, the transmitter
calculates the temperature deviation resulting from the
sensor error.
During single-point adjustment, the temperature deviation
calculated results in an offset shift of the linear
characteristic output by the linearization module; the values
of this characteristic correspond to the HART signal or are
sent to the current output.
Sensor error two-point adjustment results in a change to
the offset and gradient due to the linear temperature value
characteristic output by the linearization module.
A pure sensor offset error can be corrected via the function
"Set lower range value" or the adjustment function "Trim
low".
By contrast, if the error is not a pure sensor offset error, it
can only be corrected using two-point adjustment or two-
point calibration.
7.5.2 D/A analog output adjustment (4 and 20 mA
trim)
D/A analog output adjustment is used to compensate for
errors in the current input of the higher-level system. D/A
analog output adjustment for the transmitter can be used
to modify the loop current so that the desired value is
displayed in the higher-level system.
Error compensation for the higher-level system is possible
at the lower range value with 4 mA and / or 20 mA (single-
point error correction: offset or two-point error correction:
offset + linear gradient).
The D/A analog output adjustment can be accessed in the
DTM via the menu path "Device / Maintenance /
Adjustment".
Prior to analog adjustment, it is necessary to determine the
loop current values based on iterative entry of current
values in simulation mode; the higher-level I/O system
displays exactly 4.000 mA or the lower range limit
temperature, and 20.000 mA or the upper range limit
temperature. The current loop values must be measured
using an ammeter and recorded.
The lower range limit value or 4.000 mA +/- 16 µA must then
be simulated in D/A analog output adjustment mode using
sensor simulation. Following this, the iteratively calculated
current value at which the higher-level system displays
exactly 4.000 mA or the lower range limit value must be
entered as an adjustment value. Proceed in a similar manner
for the upper range value or 20.000 mA.
After this correction, the AD converter error of the higher-
level system is corrected by the DA converter of the
transmitter. For the higher-level system, the value of the
analog 4 ... 20 mA output signal and the digital HART signal
now match.
The adjustment should be repeated when connecting the
transmitter to another input of a higher-level system.
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