20mA and adjust R7 so the display reads "1.00". Apply 4mA and

verify that the display reads "–1.00", readjust R3 and R7 if necessary.

2. Desired display readings are:

4mA = "–450"

20mA = "450"

Use DIP-switch setting #2 in Table 2. Apply 12mA and adjust R3 so

the display reads "000". Apply 20mA and adjust R7 so the display

reads "450". Apply 4mA and verify that the display reads "–450".

Repeat adjustment procedure if necessary. For these display read

ings, no decimal points are used. Set SW4, SW5 and SW6 to OFF.

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 2. 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 adjustment

procedure if necessary.

DMS–20LCD–4/20B (Bipolar Reading Model)

The DMS-20LCD-4/20B's zero-offset circuit differs from the unipolar 'S'

model described above in that with the 'B' model, a half-scale 12mA input

is normally set to display "000". Therefore, all of the of the DIP-switch

settings in Table 2 assume a reading of "000" is desired with a 12mA input.

Display readings other than those shown in Table 2 are possible, contact

DATEL for more information.

When configuring the DMS-20LCD-4/20B for the first time, or when select-

ing a new range, set both R3 and R7 fully clockwise (roughly 22 turns) to

their minimum offset/minimum-span positions, respectively. Then select

the desired readings from Table 2 and configure DIP-switches SW1, SW2,

and SW3 accordingly.

The procedure below illustrates how to calibrate the DMS-20LCD-4/20B

to its factory-calibrated readings of "–1000" with a 4mA input and "1000"

with a 20mA input. When performing DIP-switch settings, be sure the DIP-

switch's small actuators are firmly engaged in their fully-ON or fully-OFF

positions.

1. Set both R3 and R7 fully clockwise.

2. Select DIP-switch setting #1 from Table 2.

3. Apply a precision 12mA input and adjust R3 until the meter's display

reads "000".

4. Apply a precision 20mA input and adjust R7 until the meter's display

reads "1000".

5. Apply a precision 4mA input and the display should read "–1000".

Repeat steps 3 and 4 to make sure the two adjustments did not

affect one another.

Examples (DMS-20LCD-4/20B-Bipolar Model)

1. Desired display readings are:

4mA = "–1.00"

20mA = "1.00"

Use DIP-switch setting #5 in Table 2 and enable decimal point DP2 via

SW5. Apply 12mA and adjust R3 so the display reads "0.00". Apply

Display Reading

SW1

SW2

SW3

4mA

20mA

1. 000 to 1050-1999

Off

Off

Off

2. 000 to 650-1350

On

Off

Off

3. 000 to 450-800

Off

On

Off

4. 000 to 300-500

Off

Off

On

5. 000 to 200-300

On

On

On

Table 1.

DMS-20LCD-4/20S (Unipolar Model) DIP-Switch Settings

Display Reading

SW1

SW2

SW3

4mA

12mA

20mA

1. –600 to –1000

000

600 to 1000

Off

Off

Off

2. –350 to –650

000

350 to 650

On

Off

Off

3. –250 to –400

000

250 to 400

Off

On

Off

4. –150 to –250

000

150 to 250

Off

Off

On

5. –100 to –150

000

100 to 150

On

On

On

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

The DMS-20LCD-4/20P’s Zero-Offset circuit is optimized to produce

positive readings at both 4mA and 20mA input levels. As shown in Table

3’s first three columns, a 4mA input can be typically 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 3 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 readings results in correspondingly-lower positive

readings with 4mA inputs, that is, R3’s clockwise adjustment-range is re-

duced. Example #3 below illustrates this concept. Please contact DATEL

if there is any doubt as to whether or not the DMS-20LCD-4/20P can be

configured for your display readings requirements.

When looking up DIP-switch settings in the Tables and the desired display

readings can be achieved with either of two different settings, using the higher

setting # will produce less sensitive offset (R3) and span (R7) adjustments.

Please keep in mind that the DMS-20LCD standard meter (from which the DMS-

20LCD-4/20 is derived) has an accuracy specification of ±2 counts (max.). Thus,

it may not always be possible to obtain the exact desired display reading.

12

3

4

56

ON

12

3

4

5

6

ON

12

3

4

5

6

ON

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 3 of 6

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