3. Desired display readings are:

4mA = "–650"

20mA = "650"

Notice that these readings can be obtained using either DIP-switch setting #1

or DIP-switch setting #2 in Table 3. In situations like this where DIP-switch

settings overlap, less-sensitive R3/R7 adjustments can be achieved if the

higher DIP-setting # is selected (setting #2 in this example). Apply 12mA

and adjust R3 so the display reads “000”. Apply 20mA and adjust R7 so

the display reads “650”. Apply 4mA and verify that the display reads “-650”.

Repeat adjustments if necessary.

DMS-30LCDA-4/20P (Positive-Reading)

The DMS-30LCDA-4/20P’s zero-offset circuit is optimized to produce posi-

tive readings at both 4mA and 20mA input levels. As shown in Table 4’s first

three columns, a 4mA input can be adjusted (using R3, Zero/Offset Adjust)

to display any positive reading between “000” and “800”. The corresponding

20mA-input reading is then added to the 4mA offset as a differential whose

magnitude is varied by adjusting R7 (Gain/Span Adjust).

The ‘Differential Range’ column in Table 4 lists the nominal differential display-

readings which can be obtained with R7 at, or very close to, its full-clockwise,

minimum span position. The ‘Differential Range’ column can be used as a

guide when configuring the meter for the majority of user applications. Higher

differential ranges are obtainable; however, the use of higher differential read-

ings results in correspondingly-lower positive readings with 4mA inputs, that

is, R3’s clockwise adjustment-range is reduced. Example #3 below illustrates

this point. Contact DATEL if there is any doubt as to whether or not the DMS-

30LCDA-4/20P can be configured for your display-reading requirements.

The first step when initially configuring the DMS-30LCDA-4/20P, or when

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

clockwise (roughly 22 turns each) to their minimum offset and minimum span

positions, respectively.

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

plished by subtracting the desired 4mA display reading from the desired

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

lated differential display-reading to select the appropriate DIP-switch setting

# from Table 4, configure DIP-switches SW1, SW2, and SW3 accordingly.

Please note, positions SW4 and SW5 are not used in positive reading ‘P’

models. Also, make certain that the DIP-switch’s small actuators are firmly

engaged in their fully ON or fully OFF positions.

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

which the DMS-30LCDA-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 clock-

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

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

value to select DIP-switch setting #5 in Table 4. Enable decimal point DP3 by

placing SW8 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 counterclockwise 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.

Table 4. DMS-30LCDA-4/20P (Positive Reading)

DIP Switch Settings

Desired Display Readings

Diff. Range

4mA

20mA

SW1

SW2

SW3

SW4

SW5*

1. 800 to 1400

900

1700

Off

Off

Off

NA

OFF

2. 500 to 800

850

1350

On

Off

Off

NA

OFF

3. 350 to 500

800

1150

Off

On

Off

NA

OFF

4. 250 to 350

750

1000

Off

Off

On

NA

OFF

5. 150 to 250

750

900

On

On

On

NA

OFF

5

6

7

8

1

2

3

4

ON

* Setting SW5 to On will increase the differential range.

See example 2 below.

1. Desired display readings are:

4mA ="650"

20mA = "950"

Use DIP-switch setting #4 in Table 4 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 differ-

ential 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:

Examples (DMS-30LCDA-4/20P, Positive Reading)

5

6

7

8

1

2

3

4

ON

5

6

7

8

1

2

3

4

ON

4mA =" 4.00"

20mA = "19.99"

This example illustrates the DMS-30LCDA-4/20P’s capability to display

higher differential readings than those indicated in Table 4. This example

also illustrates how the DMS-30LCDA-4/20P can be used to display the

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

0.1mA) than the example previously described.

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

in Table 4. However, use DIP-switch setting #1 in Table 4 and enable SW5

since this setting has the highest overall offset/span adjustment capabilities.

Enable DP2 via SW7, 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 necessary.

DMS-30LCDA-4/20 Series

Loop-Powered, 1.8V Drop, 4-20mA Process

Monitors with Full-Size LCD Displays

MPM_DMS30-LCDA.B02 Page 4 of 6

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