RKI Instruments GD-K77D - Manual (Page 28)

23 • Operation Model GD-K77D Operator’s Manual
4-20mA Output
The following graph illustrates the relationship between the 4-20mA output and the gas
concentration.
Figure 10: 4-20 mA output vs. Gas Concentration
Maintenance Mode
There are two maintenance modes for the Model GD-K77D: Maintenance Mode 1 and
Maintenance Mode 2. Under Maintenance Mode 1, you can perform a zero adjustment
and confirm the alarm points. Under Maintenance Mode 2, you can confirm bias voltage
(optional), perform a zero adjustment, perform a span adjustment, and determine a
sensor’s start-up time. See “Calibration” under “Maintenance” for more information about
using Maintenance Mode 2.
To activate Maintenance Mode, remove the Model GD-K77D’s cover, then press and hold
the Mode switch for three (3) seconds.
0
External output
Gas
Concentration
22mA
20mA
Maintenance mode
6% of full scale
zero suppression
2.5 mA
4 mA
Full
Scale
Measuring mode