Table 4. Decimal Point Settings

Examples (DMS-20LCD-4/20P-Positive Model)

1. Desired display readings are:

4mA = “650”

20mA = “950”

Use DIP-switch setting #4 in Table 3 since subtracting 650 from 950 yields

a differential value of 300. Apply 4mA and adjust R3 until the display reads

“000”. Apply 20mA and adjust R7 until the display reads “300” (the differen-

tial value previously calculated). Apply 4mA and adjust R3 until the display

reads “650”. Apply 20mA and verify that the display reads “950”.

2. Desired display readings are:

4mA = “4.00”

20mA = “19.99”

This example illustrates the DMS-20LCD-4/20P’s capability to display higher

differential readings than those indicated in Table 3. This example also

illustrates how the DMS-20LCD-4/20P can be used to display the output

levels of a 4-20mA loop transmitter with higher precision (0.01mA versus

0.1mA) than described above.

Subtracting 400 from 1999 yields a differential of 1599, a value not listed in

Table 3. However, use DIP-switch setting #1 in Table 3 since this setting has

the highest overall offset/span adjustment capabilities. Enable DP2 via SW5

then apply 4mA and adjust R3 so the display reads “0.00”. Apply 20mA and

adjust R7 so the display reads “15.99”. Apply 4mA and adjust R3 until the

display reads “4.00”. Apply 20mA and check to see that the display reads

“19.99” or just overranges (“1—“). Repeat adjustment procedure if neces-

sary.

Differential Range

4mA Input

20mA Input

Display Reading

SW1

SW2

SW3

SW4

SW5

SW6

DP1

DP2

DP3

1. 800-1400

900

1700

Off

Off

Off

2. 500-800

850

1350

On

Off

Off

3. 350-500

800

1150

Off

On

Off

4. 250-350

750

1000

Off

Off

On

5. 150-250

750

900

On

On

On

1

2

3

4

56

ON

12

3

4

5

6

ON

The first step when configuring the DMS-20LCD-4/20P for the first time, or

when selecting a new range, is to set R3 fully counterclockwise and R7 fully

clockwise (roughly 22 turns) to their minimum offset/minimum span posi-

tions, respectively.

The next step is to calculate the required display differential-reading; this

is accomplished by subtracting the desired 4mA display reading from the

desired 20mA display reading, disregarding decimal points. Then, using the

calculated differential display-reading to select the appropriate DIP-switch

setting # from Table 3, configure DIP-switches SW1, SW2, and SW3 accord-

ingly. Make certain that the DIP-switch’s small actuators are firmly engaged

in their fully-ON or fully-OFF positions.

The procedure below describes how to calibrate the meter for an application

which the DMS-20LCD-4/20P easily accommodates: displaying the output

of a 4-20mA transmitter, that is, "04.0" with a 4mA input and "20.0" with a

20mA input.

1. Set R3 fully counterclockwise (minimum offset position) and R7 fully

clockwise (minimum differential span position), roughly 22 turns.

2. Subtract 040 from 200 to yield a differential value of 160; use

this value to select DIP-switch setting #5 in Table 3. Enable decimal

point DP3 by placing SW6 to the ON position.

3. Set the transmitter’s output to 4.0mA and carefully adjust R3 clockwise

until the meter’s display reads “000”.

4. Set the transmitter’s output to 20.0mA and adjust R7 counterclock-

wise until the meter’s display reads “16.0”.

5. Set the transmitter back to 4.0mA and slowly adjust R3 clockwise until

the display reads “04.0”. Reapply 20.0mA and the display should now

read “20.0”. Repeat steps 3, 4 and 5 to make sure the adjustments did

not affect one another.

DMS-20LCD-4/20 Series

4-20mA Input Loop-Powered Ultra-Low 1.8V Loop Drop

3½ Digit LCD Display Process Monitors

MPM_DMS20LCD-420.B02 Page 4 of 6

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