Datel DMS-20LCD-4/20 Series Manual - Halaman 4
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DMS-20LCD-4/20
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 SW4 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.
Table 3. DMS-20LCD-4/20P (Positive Reading Model) DIP-
Switch Settings
Display Reading
Differential Range 4mA Input
1. 800-1400
900
2. 500-800
850
3. 350-500
800
4. 250-350
750
5. 150-250
750
TRANSDUCER
INPUT
+24Vdc
SUPPLY
DATEL, Inc., Mansfield, MA 02048 (USA) • Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356 • E–mail: [email protected] • Internet: www.datel.com
3 ½ D I G I T , L C D D I S P L A Y , 4 - 2 0 m A L O O P - P O W E R E D M E T E R S
SW1
SW2
SW3
20mA Input
1700
Off
Off
Off
1350
On
Off
Off
1150
Off
On
Off
1000
Off
Off
On
900
On
On
On
TRANSMITTER &
SIGNAL CONDITIONER
+
4-20mA
–
+24V
+
–
Figure 2. Typical DMS-20LCD-4/20 Connection Diagram
Examples (DMS-20LCD-4/20P-Positive Model)
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-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
necessary.
Table 4. Decimal Point Settings
SW4
DP3
PROGRAMMABLE LOGIC CONTROLLER
–
+
+
(TB1-1)
4-20mA
–
(TB1-2)
Shown for illustrative purposes only, may not be present in all applications
4
1
2
1
2
SW5
SW6
DP2
DP1
DMS-20LCD-4/20
GAIN
R7
+
A/D
Vsig
R3
–
ZERO
ON
ON
3
4
5
6
ON
ON
3
4
5
6