DMS-20LCD-4/20 Series
4-20mA Input Loop-Powered Ultra-Low 1.8V Loop Drop
3�½ Digit LCD Display Process Monitors
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.
Examples (DMS-20LCD-4/20P-Positive Model)
1.
Desired display readings are:
4mA = “650”
20mA = “950”
ON
1
2
3
4
5
6
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”
1
2
3
ON
4
5
6
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.
Table 4. Decimal Point Settings
SW4
DP1
SW5
DP2
SW6
DP3
T
able 3. DMS-20LCD-4/20P (Pos. Reading) DIP-Switch Settings
Display Reading
Differential Range
1.
800-1400
2.
500-800
3.
350-500
4.
250-350
5.
150-250
4mA Input
900
850
800
750
750
20mA Input
1700
1350
1150
1000
900
Off
On
Off
Off
On
Off
Off
On
Off
On
Off
Off
Off
On
On
SW1
SW2
SW3
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Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
MPM_DMS20LCD-420.B02
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