Xylem CR500 CIRCULAR CHART RECORDERS - Manual (Page 26)

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Probe Offset - Thermal Style (Pen Offset)
This recorder has been accurately calibrated at the factory. Before making any
adjustments, this instrument should be in service for 24 hours. Thereafter, if any
adjustment is required, perform the following procedure.
1. Place a Certified Test Thermometer(s) alongside the recorder's sensor probe(s) in
a monitored controlled condition.
2. Once the temperature has leveled out, compare the position of the pen on the
recorder to the test thermometer's reading. Also compare the Certified Test
Thermometers reading to the second pen of the recorder.
3. If an adjustment is required, for a single pen unit, depress and hold either the
LEFT (1) or RIGHT (2) arrow key. The printhead will move to current trend line
value. Using the LEFT (1) and RIGHT (2) arrow keys adjust the center scribe
mark on printhead to desired recording location. Once adjusted wait. Green LED
will go to on steady (approx. 10 sec.). Printhead will then resume normal print
operation.
4. For two (2) pen thermal recorders, you must first select the trend line that you
wish to calibrate. This is done by pressing the LEFT (1) arrow key to select trend
for pen 1 or the RIGHT (2) arrow key to select trend for pen 2. Hold the selected
key until green LED goes out. Then release the key. The green LED will begin to
flash. The printhead will now move to the current trend line value. Using LEFT
(1) and RIGHT (2) arrow keys adjust the center scribe mark on printhead to
desired recording location. Once adjusted, wait. Green LED will get to on steady
(approx. 10 sec.). Printhead will then resume normal print operation.
The remaining pen can now be selected and adjusted, if necessary using
instructions above.
NOTE: if unit has optional display, display will indicate the OFFSET value.
Thermal Print Contrast Adjustment
If print recording is light, the contrast can be darkened by the following procedure.
Please note the darker the print setting can shorten printhead life span. Adjust only if
print contrast is needed to improve readability.
1. Remove power from instrument.
2. Prior to powering up depress and hold the Change Chart (3) key.
3. While holding key, power instrument up.
4. Upon power up, release key. Pen will travel full upscale. Pen will then begin to
sweep across chart printing a line with current contrast value.
5. Depress and hold LEFT arrow (1) key to DECREASE contrast. Depress and hold
RIGHT arrow (2) key to INCREASE contrast.
6. Once contrast setting is acceptable, depress the Change Chart (3) key to store
contrast setting.
7. Unit will begin recording properly with new setting applied.