Emerson Process Management 53eA instruction manual Section

MODEL 54eA	SECTION 15.0
	CALIBRATION - CONTROL

concentration, temperature) compared to the measurement range, the difference between the 20 mA (Hi) and 4 (or 0) mA (Lo) setpoints, which you determined when configuring the analog output.

In the example shown in Figure 15-1:

The percent change in pH was:

pH2 - pH1	x 100% =	8.2 - 7.2 pH	= 33.3%
pH “Hi” - pH “Lo”		9.0 - 6.0 pH

The change in the output signal was:

6 - 4 milliamps x 100% = 12.5%

20 - 4

So the Plant Gain is:

C = 33.3 = 2.66 12.5

Once R and C are calculated, the proportional and integral bands can be determined as follows:

C

Proportional band (%) = P = 286 R

Integral Time (seconds per repeat) = I = 3.33 x D x C

So for the example:

286 (2.66)

P = = 254% 3

I = 3.33 (4 sec.) 2.66 = 36 seconds

To enter these parameters, use the procedure detailed in Section 5.6.

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