Revision 1
STT700 Series HART/DE Option User’s Manual
Page 69
6.5 Calibrating Range Using the MC Toolkit
The range calibration involves two procedures, one to calibrate the input, the other to calibrate the
output. This section provides details on both procedures.
6.6 Conditions for Input Calibration
Calibrate the transmitter input only when necessary, and under conditions that will ensure accuracy:
Remove the transmitter out of service, and move it to an area with favorable environmental conditions,
for example, clean, dry, and temperature-controlled
The source for the input temperature must be precise, and certified for correct operation.
Qualified personnel are required for the input calibration procedure.
To optimize accuracy, the PROM includes storage for calibration constants: Correct LRV, and Correct
URV. These constants provide for optimum accuracy in that they enable fine-tuning of the input
calculations by first correcting at zero input, then by bounding the input calculations at the selected
operating range. Corrections are applied at the Lower Range Value (LRV) and the Upper Range Value
(URV).
Factory calibration can be specified when you order your transmitter. Also, if precision equipment,
suitable environment, and required skill are available at your site, input calibration can be done locally.
The procedure requires a precision temperature source with an accuracy of 0.04% or better to do a
range calibration. Factory calibration of the STT700 temperature transmitter is accomplished with
inches-of- water ranges referenced to a temperature of 39.2 °F (4°C).
6.7 Input Calibration Procedures Description
The input calibration process consists of the following three parts:
Correcting the input LRV.
Correcting the input URV.
For the input calibration procedure, current loop component tolerances and values are not
critical if they support reliable communication between the transmitter and the MC Toolkit.
Refer to the STT700 SmartLine Tr
ansmitter User’s Manual, 34-TT-25-17.
For the input calibration procedures, connect the test setup illustrated in Figure 11. Either voltage
mode (voltmeter across the resistor) or current mode (ammeter in series with the resistor) is
satisfactory.