Emerson IFT9701 instruction manual Milliamp output performance

Power Supply and Output Wiring continued

4.4.1Milliamp output

The 4–20 mA output is an active output that can represent the mass or volume flow rate. At the factory, the output is configured to represent the range of flow rates that are measured in the application. The milliamp output is active, does not require external power, and has the following features:

•Can supply any loop-powered process indicator.

•Isolated to ±500 VDC from all other outputs and earth ground.

•Requires loop resistance of 250 to 600 ohms to produce digital signals for communication via HART protocol.

•For milliamp output, the negative terminal can be grounded or left floating. If the output communicates via HART protocol, the negative terminal should be grounded for optimal performance.

Milliamp output performance is described below and illustrated in Figure 4-3.

CAUTION

Milliamp output range has changed.

Milliamp outputs will not output live signals between 2.0 and 3.8 mA, or between 20.5 and 22 mA.

Systems that rely on milliamp output signals in the ranges listed above might not perform as expected. For IFT9701 transmitters shipped after October 1999, outputs will saturate at 3.8 and 20.5 mA, unlike previous versions of IFT9701 transmitters.

Reconfigure systems as necessary.

In compliance with the NAMUR NE43 standard:

•To represent process data, the milliamp output will produce a live signal in the range of 3.8–20.5 mA.

•The milliamp output will never produce a signal in the range of 2.0–3.8 mA, or in the range of 20.5–22 mA.

•To indicate a fault, the milliamp output will produce a signal of 2 or 22 mA. The fault output level is determined by the fault-output jumper setting — downscale or upscale — as described in Section 2.3.2.

Figure 4-3 Milliamp output performance

Downscale	Upscale
fault indication level	fault indication level

Operating range (live signal)

2	3.8	20.5	22
		Output in mA

22 Model IFT9701 Transmitter Instruction Manual