SCADAPack Transmitters

This Technical Support Notice describes how to use the analog outputs on 4000 Series transmitters equipped with analog outputs.

4202GFC-DS

The 4202GFC - DS includes one 0-20mA current sinking analog output. Refer to the appropriate software manual for information on using the 4202GFC Analog Output in an application programs. For TelePACE applications refer to the Register Assignment for the 4202GFC I/O module and for ISaGRAF applications refer to the I/O Complex Equipment for 4202GFC I/O.

When a sinking analog output is wired to an external device care must be taken to ensure the operating characteristics of the analog output are considered. As can be seen in Figure 1: Analog Output Wiring the LOAD does not connect to ground at any point. The LOAD must be able to float above ground in order for the analog output to function. The analog output must be connected to a differential input device.

For example, in the wiring example shown in Figure 1, the points A and B will each be at a positive voltage based on the sinking current output, the LOAD resistance and the Power Supply voltage.

  • For a sinking current of 0 mA, a LOAD resistance of 250 Ohms and a power supply voltage of 24VDC the voltage at both A and B points is 24VDC.
  • For a sinking current of 20 mA, a LOAD resistance of 250 Ohms and a power supply voltage of 24VDC the voltage at point B is 24VDC and the voltage at point A is 24VDC minus 5VDC (20 mA x 250 Ohms) or 19VDC.

NOTE: The LOAD cannot be connected to ground in any wiring configuration for the analog output.

Figure 1: Analog Output Wiring

4000 Series MMT and MPT Transmitters

Some versions of the 4000 Series transmitters have a single 0-20mA current sinking analog output. The analog output is either associated with the built-in PID controller, or may be used as a general purpose analog output. The analog output accepts SCADAPack standard signed 16-bit integer output values. Valid values are -8192 to 32767, which represent 0 to 20mA output. A value of 0 represents 4mA.

When a sinking analog output is wired to an external device care must be taken to ensure the operating characteristics of the analog output are considered. As can be seen in Figure 2: Analog Output Wiring the LOAD does not connect to ground at any point. The LOAD must be able to float above ground in order for the analog output to function. The analog output must be connected to a differential input device

For example, in the wiring example shown in Figure 10, the points A and B will each be at a positive voltage based on the sinking current output, the LOAD resistance and the Power Supply voltage.

  • For a sinking current of 0 mA, a LOAD resistance of 250 Ohms and a power supply voltage of 24VDC the voltage at both A and B points is 24VDC.
  • For a sinking current of 20 mA, a LOAD resistance of 250 Ohms and a power supply voltage of 24VDC the voltage at point A is 24VDC and the voltage at point B is 24VDC minus 5VDC (20 mA x 250 Ohms) or 19VDC.

NOTE: The LOAD cannot be connected to ground in any wiring configuration for the analog output.

Figure 2: Analog Output Wiring