Metex 8760CLP Total Free Chlorine & pH Analyzer - Manual (Page 56)

AQUAMETRIX INC.
1-800-742-1413 www.aquametrix.com
56
Adjusting Electronic Calibration
1. Outputs are isolated from main circuit, therefore, measurements are made with common at the output
2 terminal, TB304.
2. Measure output 1 ‘zero’ at TP301 (pin 8 of U304), while output 1 is outputting 4.00 mA. Reading
should be between -0.870 V and -1.250 V. Adjust #2 voltage with VR300.
3. Change analyzer output to 20.00 mA, switch meter to mA and measure + Terminal (+ terminal of
O/P 1) and adjust VR301 so that the current reads 20.00 mA. Return analyzer output to 4.00 mA and
trim actual output to 4.00 mA using VR300. Check again at 20.00 mA and repeat adjustments until
satisfied.
4. Measure output 2 zero at TP300 (pin 7 of U304), while output 2 is outputting 4.00 mA. The test
point should read between -0.870 V and -1.250 V. Adjust #2 ‘zero’ voltage with VR302.
5. Change output at output 2 to 20.00 mA, switch meter to mA at TB304, + terminal of output 2, and
adjust VR303 (span pot) until the current reads 20.00 mA.
NOTE: Zero and span are very wide range adjustments which show small interactions. Recheck
zero and span to confirm good calibration.
6. If so desired, all software settings can be returned to factory default condition by performing a
reinitialization. Refer to heading Initializing All Program Settings in Configuration of Program
section.
Testing Relay Outputs
1. Relay output operation can be verified by testing for contact closure or continuity at each relay. To
activate a relay, select [CONF] [NO.NC] [AL.A] from the menu. Press ENTER to go into edit mode,
then press the Up or Down arrow key to change the normally open/normally closed configuration
from open to closed. Press ENTER again to accept the new value. A closed contact should open, an
open contact should close.
2. Repeat step 1 for for the Alarm B contact.
3. If so desired, all software settings can be returned to factory default condition by following the
procedure in Re-initializing All Settings in the Configuration of Program section.
Chlorine Sensor
Slow Response — typically due to excessive sample line length and low flow, thus producing long
sample transport lags. Resolve by adding a fast-flow loop with the sensor in a short side stream, or by
shortening the line. Slow response can also be caused by growth of biologicals in the sample line. In
this case, the problem may be alleviated by changing the take-off point.
Readings consistently low or spike low — characteristic of wiring problems between the analyzer and
the chlorine sensor; an open circuit in the field wiring will result in zero cell current and a very low
reading. Review the installation instructions.
Readings gradually falling — the analyzer can no longer be calibrated properly. This problem is
typical of sludge/slime deposits on the face of the chlorine sensor. The sensor will need to be cleaned.
Refer to the Monthly Maintenance and/or Semi-Annual Maintenance procedure in this manual.
Readings trend higher — this problem is typical of pressure gradually stretching the chlorine sensor
membrane which is getting thinner. The membrane will soon fail. Correct by lowering pressure at the
sensor. Change membrane if required.