D-Guard
2
56
18.
APPENDIX A:
18.1.
Output Current Signal - Total Loop Resistance vs Power Supply Voltage
The maximum total current loop load resistance that can be driven by D-Guard
2
depends on the voltage supply fed to
the detector. This total resistance includes all aspects of an installation such as barrier resistance, cable resistance /
length and the value of the sense resistor used at any connected controller's input channel.
The operator is advised to account for all of these system resistances and provide a source of power supply that will
allow the detector to operate safely with the ability to drive the loop to 22mA (fault signalling).
Incorrect allowance for system resistances and power supply voltages may result in the detector being unable to
correctly signal the measured gas concentration.
The graphs below show the relationship between detector power supply voltage output and maximum loop resistance
for both Group I and Group II versions of D-Guard
2
. Note that there are two graphs for each type since the detector
can be configured prior to installation to use the display backlight or not. Disabling the backlight allows a wider range
of supply voltages and loop resistances.
18.1.1
Loop Resistance - Group I D-Guard
2
With Backlight Disabled - loop at 22mA
18.1.2
Loop Resistance - Group I D-Guard
2
With Backlight Enabled - loop at 22mA
Summary of Contents for D-Guard2
Page 2: ...D Guard2 1 This Page Left Intentionally Blank ...
Page 65: ...D Guard2 62 23 APPENDIX F 23 1 System Menu Map ...
Page 68: ...D Guard2 65 25 APPENDIX H Product Certificates 25 1 IECEx Product Certificate ...
Page 69: ...D Guard2 66 ...
Page 70: ...D Guard2 67 ...
Page 71: ...D Guard2 68 ...
Page 72: ...D Guard2 69 25 2 ATEX Product Certificate ...
Page 73: ...D Guard2 70 ...
Page 74: ...D Guard2 71 ...
Page 75: ...D Guard2 72 ...
Page 76: ...D Guard2 73 26 APPENDIX I Product Dimensions ...
Page 77: ...D Guard2 74 Doc_Rev 03 12 15 ...