Sierra Monitor Corporation 4105 manual Appendix a Unity Gain Mode

Instruction Manual

Appendix A: Unity Gain Mode

The Unity magnetic control is available during CAL MODE to allow the ZERO and SPAN adjustments to be centered within their range. This is similar to setting a potentiometer so the wiper terminal is exactly halfway between the clockwise and counterclockwise terminals. this is identified as the UNITY GAIN mode. In UNITY GAIN the ZERO controls have a ± 15% of full scale adjustment range. For example, in UNITY GAIN, if the sensor's ZERO output has drifted so high that it reads 15% with ZERO gas applied, the DOWN ZERO magnetic control could still bring the 4105-XX reading to ZERO. However, it will be at the end of its adjustment range. If the ZERO adjustment required is greater than ±10% of full scale, a BALANCE adjustment should be performed as described in Appendix A.

In UNITY GAIN the SPAN controls have a .5 to 2 adjust- ment range. For example, in UNITY GAIN, if a sensor's output sensitivity has been reduced to the point where 50% SPAN gas provides only a 25% reading, the UP SPAN magnetic control could still calibrate the reading to the proper value of 50%. However, it will be at the end of its adjustment range.

Appendix B: L.C.D. Readout Calibration Procedure

The 3 1/2 digit LCD meter span and decimal points may be configured for full scale ranges such as 1- 100, 0-25, 0-10.0, 0-1000 and many others. Zero per- cent of full-scale readings, or those corresponding to 4mA, are always assumed to equal a reading of 0. Holding the magnet over the CAL key for at least 5 seconds enters the LCD METER SPAN SETUP MODE. After this, the current setting for 100% full scale is displayed and may be modified using the UP/ DOWN SPAN keys. This sets the LCD reading dis- played when the 4-20mA output equals 30mA. Deci- mal points are added with the UNITY key.

Appendix C: End of Sensor Life Indication

Old sensors near the end of their service life require higher gain settings. M4105-XX "END OF SENSOR LIFE" (ESL) feature may be used to indicate condi- tion. A span trip point may be entered that when ex- ceeded, causes the LCD to flash and ESL reading for 2-seconds each 10 seconds. Holding the magnet to the UNITY key for at least 5 seconds brings the LCD

aspan value set-point reading for setting when the ESL indication trips. CAL MODE GAIN adjustments range between .5 and 2 and the ESL set-point is ad- justable between 1.5 and 2.01 with 2.01 turning the ESL feature off. The current span setting may be viewed on the LCD during NORMAL MODE by touching the DOWN SPAN key.

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