Doc#
M9344 • REV K
(April 2022) Page
6 of 8
Set the current loop to the zero current reading of the transmitter and adjust the ZERO (R7)
control for a reading of 0.00. Next set the current loop to the full scale current value and
adjust the SPAN (R6) control for the proper indication. Alternately adjust the ZERO and SPAN
controls as adjustments interact.
Label Full Scale
Reading
1.0 in/s
1.00
19.9 mm/s
19.9
100 mm/s
100
NOTE:
If a voltage source is used to generate a
current, a load resistance must be connected
in series with the ST5491E indicator module.
Failure to do so may damage the unit.
After calibration, reassemble the module, reconnect the wiring, and reassemble the unit.
CALIBRATION
The ST5491E transmitter has been factory calibrated for the full scale vibration level marked on
the label. If the calibration is in doubt the unit can be verified in the field by following the pro
-
cedures outlined below. Note that there are no Zero and Span adjustments on the transmitter.
1. Zero Verification
In the absence of vibration the output current should be 4 mA ±0.1 mA.
If the ambient vibration is more than 2% of full scale, the transmitter should be removed from
the machine and placed on a vibration free surface for this measurement. Often a piece of
foam can be used to isolate the transmitter from external motion.
2. Span Verification
Subject the transmitter to a known vibration within the full scale range
marked on the label. If using a portable vibration shaker where it can be tested at full scale,
the output should be 20 mA ±0.4 mA. If using another reference, like a similar machine, calcu
-
late the current value on a proportional basis.
The output level can also be compared to a vibration level read on a portable vibration meter.
This reading should be taken as close to the transmitter location as possible.
If you shake the transmitter by hand you can produce a high output as long as there are no
high pass filters. Check the configuration for filters. There is no way of knowing the expected
output when shaking it by hand.
3. Digital Indicator
Calibration of the Digital Indicator requires partial disassembly of the
ST5491E. Remove the Digital Indicator threaded cover. Carefully remove the electronics mod
-
ule using a small flat head screwdriver. Note how the transmitter wires are connected before
disconnecting them. Remove the retaining wire from the bottom of the module and carefully
remove the electronics board assembly from the module housing. Connect the electronics
module is series with a current loop that can be accurately set from 4.0 mA to 20.0 mA +/- 0.1
mA.
