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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 4 of 6
1
2
3
4
5
6
ON
1
2
3
4
5
6
ON
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 differential 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-20PC-4/20P’s capability to display
higher differential readings than those indicated in Table 3. This
example also illustrates how the DMS-20PC-4/20P can be used to
display the output levels of a 4-20mA loop transmitter with higher preci-
sion (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 necessary.
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.
Examples (DMS-20PC-4/20P-Positive Model)
Table 3. DMS-20PC-4/20P (Positive Reading Model)
DIP-Switch Settings
Differential Range 4mA Input
20mA Input
Display Reading
SW1 SW2 SW3
Table 4. Decimal Point Settings
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
fully clockwise (roughly 22 turns) to their minimum offset/minimum span
positions, 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, confi gure DIP-switches SW1, SW2, and
SW3 accordingly. Make certain that the DIP-switch’s small actuators are
fi rmly engaged in their fully-ON or fully-OFF positions.
The procedure below describes how to calibrate the meter for an applica-
tion which the DMS-20PC-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.
