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Getting Started Model GFC7001E Carbon Dioxide Analyzer
Teledyne Analytical Instruments 39
3.3.2. ANALOG OUTPUT CONNECTIONS
The GFC 7001E is equipped with several analog output channels accessible through a connector on the back
panel of the instrument. The standard configuration for these outputs is mVDC. An optional current loop output
is available for each.
When the instrument is in its default configuration, channels A1 and A2 output a signal that is proportional to the
CO concentration of the sample gas. Either can be used for connecting the analog output signal to a chart
recorder or for interfacing with a datalogger.
Output A3 is only used on the GFC 7001E/EM if the optional CO
2
or O
2
sensor is installed.
Channel A4 is special. It can be set by the user (see Section 7.4.6) to output any one of the parameters
accessible through the <TST TST> keys of the units sample display.
To access these signals attach a strip chart recorder and/or data-logger to the appropriate analog output
connections on the rear panel of the analyzer.
A
NALOG OUT
A1
A
2 A3 A4
+ - + - + - + -
Figure 3-7: Analog Output Connector
Table 3-4: Analog Output Pin-Outs
PIN ANALOG OUTPUT VOLTAGE SIGNAL CURRENT SIGNAL
1
A1
V Out I Out +
2 Ground I Out -
3
A2
V Out I Out +
4 Ground I Out -
5
A3
(Only used if CO
2
or
O
2
Sensor is
installed)
V Out I Out +
6 Ground I Out -
7
A4
V Out I Out +
8 Ground I Out -
3.3.3. CONNECTING THE STATUS OUTPUTS
The status outputs report analyzer conditions via optically isolated NPN transistors, which sink up to 50 mA of
DC current. These outputs can be used interface with devices that accept logic-level digital inputs, such as
Programmable Logic Controllers (PLCs). Each status bit is an open collector output that can withstand up to 40
VDC. All of the emitters of these transistors are tied together and available at D.
NOTE
Most PLC’s have internal provisions for limiting the current that the input will draw from an external
device. When connecting to a unit that does not have this feature, an external dropping resistor must be
used to limit the current through the transistor output to less than 50 mA.
At 50 mA, the transistor will drop approximately 1.2V from its collector to emitter.