Emerson Process Management 1500 manual 6.5Configuring cutoffs, 1 Cutoff default values

Optional Transmitter Configuration

8.Define the standard density to be used in calculations.

•To use a fixed standard density, click the top radio button, enter a value for standard density in the Standard Density textbox, and click Next.

•To use a calculated standard density, click the second radio button and click Next. Then enter values for Reference Temperature, Reference Pressure, and Specific Gravity on the next panel, and click Next.

9.Check the values displayed.

•If they are appropriate for your application, click Finish. The special unit data will be written to the transmitter.

•If they are not appropriate for your application, click Back as many times as necessary to return to the relevant panel, correct the problem, then repeat the above steps.

6.5Configuring cutoffs

Cutoffs are user-defined values below which the transmitter reports a value of zero for the specified process variable. Cutoffs can be set for mass flow, volume flow, or density.

See Table 6-1for cutoff default values and related information. See Sections 6.5.1 and 6.5.2 for information on how the cutoffs interact with other transmitter measurements.

Table 6-1Cutoff default values

Cutoff type	Default	Comments
Mass flow	0.0 g/s	Recommended setting: 0.5–1.0% of the sensor’s rated maximum flowrate
Volume flow	0.0 L/s	Lower limit: 0
		Upper limit: the sensor’s flow calibration factor, in units of L/s, multiplied by 0.2
Density	0.2 g/cm3	Range: 0.0–0.5 g/cm3

6.5.1Cutoffs and volume flow

The mass flow cutoff is not applied to the volume flow calculation. Even if the mass flow drops below the cutoff, and therefore the mass flow indicators go to zero, the volume flow rate will be calculated from the actual mass flow process variable.

However, the density cutoff is applied to the volume flow calculation. Accordingly, if the density drops below its configured cutoff value, both the reported density and the reported volume flow rate will go to zero.

6.5.2Interaction with the AO cutoff

The mA output also has a cutoff – the AO cutoff. If the mA output is configured for mass or volume flow:

•And the AO cutoff is set to a greater value than the mass and volume cutoffs, the flow indicators will go to zero when the AO cutoff is reached.

•And the AO cutoff is set to a lower value than the mass or volume cutoff, the flow indicator will go to zero when the mass or volume cutoff is reached.

See Section 4.5.3 for more information on the AO cutoff.

38 Micro Motion® Model 1500 Transmitters with the Filling and Dosing Application