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QuadGard Installation and Operating Manual. Issue 5. January 1996Page15

Dräger QuadGard - 20351 4.3Set range, gas name and measurement units

Set the name of the gas being measured using channel command 04–0. For SE Exchannels it is recommended that the gas name be set to “Ex”.Set the measurement unit using channel command 04–1. Set the measurement range using channel command 04–2. The range of each card must be the same as the measuring head to which it is connected,otherwise the reading displayed by the card will not correspond to the gas concentrationbeing measured by the head.

4.4Set alarm trip points

Always set the alarm trip points after setting the measurement range, because changingthe range resets the alarm trip points to 20% and 40% of full-scale.Set the A1 alarm level using channel command 11–1. Set the A2 alarm level using channel command 11–2. Set rising or falling alarms using channel commands 11–4 and 11–5.

4.5Set zero

4.5.1Set zero for 4–20mA channels Zero can be adjusted by ±1mA from 4mA.1.Select channel command 10–0.2.While there is no gas at the measuring head, use and to set the display to zero.If the display is still above zero and pressing displays “MINIMUM”, this indicatesthat the signal from the measuring head is too high to set zero; if the display isnegative and pressing displays “MAXIMUM”, this means that the signal from thehead is too low. Check the measuring head and re-calibrate it if necessary.3.When the display reads zero, press Reset. 4.5.2Set zero for SE Ex channels Zero is set by automatic adjustment (balancing) of the electronic 'bridge', compensatingfor an imbalance of up to 100mV.1.Select channel command 10–0. The display will show “DO NOTHING”.2.While there is no flammable gas at the measuring head, use or to change thedisplay to “BALANCE Ex HEAD” and press Reset.3.Wait for the bridge balance point to be found, after which the display will show“BALANCE OK”.A display of “TOO LOW” or “TOO HIGH” indicates that the heads zero error is toogreat. Check the head and/or the connections.A display of “BALANCE FAILED” indicates that the signal from the head haschanged during the zero routine. Allow the head to settle before trying to zero again.