Emerson IFT9701 사용자 설명서

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 continued

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.

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.

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.