SMAR TT301, Operation, Maintenance & Instruction Manual

Page: 35 / 74

Programming Using Hand-Held Terminal
3.9
Calibrating the TT301
A transmitter calibration consists of configuring the input values related to 4 mA and 20 mA. The
TT301
may do this in 4 different methods:
1
– By using the Configurator (no-reference method) whose calibration input is not required.
2
– By using the Configurator and an input signal as reference (referenced method).
3
– Local adjustment and an input signal as reference (simple local adjustment, with reference).
4
– Local adjustment and an input signal as reference (complete local adjustment, with reference).
5
– Local adjustment (complete local adjustment, without reference).
In transmitter mode, the lower value always corresponds to 4 mA and the upper value to 20 mA. In PID
mode, the lower value corresponds to PV=0 % and upper value to PV=100 %.
Calibration Without Reference
The
TT301 may be configured to supply 4 to 20 mA, the equivalent to the temperature limits on the
user’s application, without the need to connecting a reference calibrating generator on its terminals.
This is possible because the
TT301 has linearization curves for several standard temperature
sensors in its memory. Let us suppose the transmitter range is calibrated from
–100 to 300
o
C and
one must calibrate it on 0 to 100
o
C.
The transmitter generates a signal varying from 4 to 20 mA when the temperature oscillates between 0
and 100
o
C.
Watch that both the LOWER and UPPER values are entirely independent. Adjusting one does not
affect the other. However, the following rule must be observed:
a) Both values should not be less than the lower limit or in excess of the upper calibration limit.
b) The Upper value less Lower value span must be larger than the LOWER SPAN.
If a signal needs to be reverted, i.e., have an UPPER VALUE smaller than the LOWER VALUE,
proceed as follows:
Make the inferior value as close as possible to the Superior Value or vice-versa, observing the allowed
minimum span. Adjust the Superior Value with the desire value and, then, adjust the Inferior value.
Example: If the transmitter is calibration such as:
LOWER VALUE = 4 mA = 0
o
C
UPPER VALUE = 20 mA = 100
o
C and the values should change to:
LOWER VALUE = 4 mA = 100
o
C
UPPER VALUE = 20 mA = 0
o
C;
Considering that the Pt100 IEC Minimum Span is 10
o
C, the adjustments must be altered as follows:
a) LOWER VALUE = 90, or 100-10.
b) UPPER VALUE = 0
o
C
c) LOWER VALUE = 100
o
C
The table 3.4 shows graphycaly how to do this ranging.