EX-5120
ENMET Corporation
9
5.2 Calibration of the EX-5120
Calibration is the process of setting the instrument up to read accurately when exposed to a target gas. The Zero function sets
the clean air reference point and the Span function sets the sensitivity of the instrument.
Initial Calibration:
Wait several minutes for stabilization after supplying power to the
EX-5120
sensor/transmitter (S/T)
before initial calibration. The S/T has been precalibrated at the factory, and initial field calibration should result in only fine
tuning to circuit, as well as a way to check that installation is successful. It is not necessary to open the enclosure to make
adjustment. The calibration functions are operated with magnets from outside the enclosure through the
MENU
and
SELECT
switches. Do Not open the S/T unless the area is de-classified.
Calibration Zero and Span functions are two separate procedures. They operate independently of each other. It is
recommended that the Zero procedure be done prior to the Span procedure.
ENMET
Corporation recommends at least
quarterly calibration of the
EX-5120
transmitters.
Calibration equipment is available from
ENMET
Corporation to calibrate the
EX-5120
sensor/transmitters. A calibration
adapter will have a fitting for the gas cylinder on one side, and a cover to go over the sensor housing on the other.
Generally, a cylinder of 20.9% Oxygen is used to provide a fresh air reference or Zero point for the calibration. Another
cylinder is used to provide the Span reference point for calibration. Depending on the instrument calibration, the Span gas may
be the same gas that the instrument is calibrated to display, or it may be another gas, which
ENMET
has found to have a similar
response.
Figure 4: Calibration Adapter EX-5120 Sensor/Transmitter
5.2.1 Zero Adjust
A ZERO function should be performed only when the
EX-5120
sensor/transmitter is exposed to fresh air. If the air at the sensor
is in question, use a cylinder of 20.9% oxygen to provide a clean air reference. Attach the cylinder to the calibration adapter.
Enter the maintenance menu by placing the magnet over
M
ENU
switch for 2 to 4 seconds. See
Figure 5,
EX-5120
Maintenance Menu flow chart.
The second menu available is the Zero.
Tap the
S
ELECT
switch to perform a Zero.
If the Zero is successful, Cal OK appears on the display and in 1 – 2 seconds, display will change to Span.
If you wish to Span the sensor Tap the
S
ELECT
switch you are now ready to apply gas.
Proceed to gas span step 2
If you wish to Exit the maintenance menu, Tap
M
ENU
switch until Exit is displayed, then tap
S
ELECT
switch to return to the
instrument Normal Gas Display
If the Zero is Not successful, sensor is outside of safe parameters to be zeroed, the display will read Bad Zero. Repeat
Section 5.2.1 Zero Adjust making sure to use a cylinder of 20.9% Oxygen.
Regulator
Gas Cylinder
Select
Menu
Output, for Gas
Input, for Calibration
or Optional Gas Sampling
Calibration Cover