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DMS-20PC-4/20 Series
Subminiature 4-20mA Loop-Powered
3½ Digit LED Process Monitors
MPM_DMS20PC-4/20.D01 Page 3 of 6
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DMS–20PC–4/20B (Bipolar Reading Model)
The DMS-20PC-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
Murata Power Solutions for more information.
When configuring the DMS-20PC-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-20PC-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-20PC-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
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 readings, 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.
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
Table 2. DMS-20PC-4/20B (Bipolar Model) DIP-Switch Settings
DMS-20PC-4/20P (Positive Reading Model)
The DMS-20PC-4/20P’s Zero-Offset circuit is optimized to produce posi-
tive 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 read-
ings with 4mA inputs, that is, R3’s clockwise adjustment-range is reduced.
Example #3 below illustrates this concept. Please contact Murata Power
Solutions if there is any doubt as to whether or not the DMS-20PC-4/20P
can be configured for your display readings requirements.
The first step when configuring the DMS-20PC-4/20P for the first time, or
when selecting a new range, is to set R3 fully counterclockwise and R7
3. Desired display readings are:
4mA = ".000"
12mA = ".250"
This example is not as straightforward as the previous two. Notice that
12mA is exactly halfway between 4mA and 20mA. If we assume that
the input could go up to 20mA, the display reading would then be: 2
x .250 or ".500". From Table 1 we can now select DIP-switch setting
#4 and enable DP1 via SW4. Apply 4mA and adjust R3 so the display
reads ".000". Apply 12mA and adjust R7 so the display
reads ".250".
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