DATEL, Inc., Mansfield, MA 02048 (USA)
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Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356
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E-mail: [email protected]
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Internet: www.datel.com
DMS-40LCD-4/20S
Ultra-Low 2.9V Loop-Drop
4½ Digit LCD-Display
Process Monitor
Figure 1. DMS-40LCD-4/20S Simplified Schematic
Features
®
®
The DMS-40LCD-4/20S’s ultra-low 2.9V typical loop-drop (190-Ohm burden) makes it
ideal for use in 4-20mA process monitoring applications which have two or more series-
connected loop-monitoring devices. The low loop-burden means it can be used in current
loops that are powered from supply voltages as low as +8Vdc! The DMS-40LCD-4/20S is
self-powered; all required operating power is derived directly from the current loop itself. It
requires no separate dc power supply or special grounding considerations and can be
connected ANYWHERE in the loop!
The DMS-40LCD-4/20S's input, span, and offset circuits all employ super-stable,
±0.5% thin-film chip resistors. Long-term stability and accuracy are assured by driving
these tight-tolerance resistors with an ultra-stable, ±0.2% band-gap voltage reference.
Unlike many competitor’s designs, the two precision 20-turn span and zero adjust
potentiometers do not interact with one another. Its full-size, 0.40" (10.0mm) high-
contrast 4½ digit LCD display offers 19,999 counts of resolution and can be read in
virtually any lighting condition—including full sunlight!
All range-change and decimal point selections are made by configuring two gold-
plated, vibration-resistant, six-position DIP switches. The two connections to the
current loop are made via a reliable, screw-type terminal block. To further enhance
reliability, the design features 100% soldered connections—no troublesome zebra/
elastomercic connectors are used. All these outstanding features make the DMS-
40LCD-4/20S the highest quality, most rugged, 4½ digit, LCD-display process monitor
available.
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Loop-powered, no power supply required!
•••••
2.9V typical loop-drop; 190-Ohm (max.) loop
impedance
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Dip-switch-selectable range, offset, and
decimal points
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Hundreds of different input/readout
combinations
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Non-interacting gain (span) and offset (zero)
20-turn potentiometers
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Large, 0.40" (10.0mm) high, sunlight-viewable
LCD digits
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Miniature size: 2.17" x 0.92" x 0.90" (55mm x
23mm x 23mm)
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Vibration-resistant package; reliable screw-
terminal connections
•••••
100% soldered connections
DATA
4½ DIGIT A/D
CONVERTER
DP3
DP2
DP1
ZERO
ADJUST
GAIN
ADJUST
CURRENT TO
VOLTAGE
CONVERTER
DP4
R3
R7
Range
Offset
Gain
S1
S2
ON
ON
1
1
1
2
3
4
5
6
2
3
4
5
6
ON
ON
1
1
1
2
3
4
5
6
2
3
4
5
6
+
–
TB1
4-20mA
–
+
DC/DC
CONVERTER
BAND-GAP
REFERENCE
CIRCUIT
+5V
–5V
1
2
Current Loop Input
Actual Size
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