DMD4059 Series Strain Gauge to DC Isolated Transmitter
3
Device Connected to Output Terminal Terminal Switch E
Voltage input
3 (
–)
4
(
+)
V
Passive mA (current) input.
Module provides loop power
3 (
–)
4
(+20 V)
I
mA (current) input device that
provides loop power.
2 (
–)
3
(
+)
I
Output Test Function
When the test button is depressed it will drive the output with a
known good signal that can be used as a diagnostic aid during
initial start-up or troubleshooting. When released, the output will
return to normal.
The Test Cal. potentiometer can be used to set the test output
to the desired level. It is adjustable from 0 to 100% of the
output span.
Press and hold the Test button and adjust the Test Cal. potenti-
ometer for the desired output level.
Installation Precautions
WARNING! Avoid shock hazards! Turn signal input, output, and
power off before connecting or disconnecting wiring, or remov-
ing or installing module.
Mounting to a DIN Rail
The housing clips to a standard 35 mm DIN rail. The housing is
IP40 rated and requires a protective panel or enclosure.
Do not block air flow. Allow 1” (25 mm) above and below hous-
ing vents for air circulation.
1. Tilt front of module downward and position against DIN rail.
2. Clip lower mount to bottom edge of DIN rail.
3. Push front of module upward until upper mount snaps into
place.
Removal
1. Push up on the bottom back of the module.
2. Tilt front of module downward to release upper mount from
top edge of DIN rail.
3. The module can now be removed from the DIN rail.
Operation
Strain gauges and load cells are normally passive devices that
are commonly referred to as “bridges” due to their four-resistor
Wheatstone bridge configuration. These sensors require a
precise excitation source to produce an output that is directly
proportional to the load, pressure that is applied to the sensor.
The exact output of the sensor (measured in millivolts) is deter-
mined by the sensitivity of the sensor (mV/V) and the excitation
voltage applied.
An additional input, the sense lead, monitors the voltage drop in
the sensor leads and automatically compensates the excitation
voltage at the module in order to maintain a constant excitation
voltage at the sensor.
The DMD4059 provides the excitation voltage to the sensors and
receives the resulting millivolt signal in return. This input signal
is filtered and amplified, then offset, if required, and passed
to the output stage. Depending on the output configuration
selected, a DC voltage or current output is generated.
The green input LED provides a visual indication that a signal
is being sensed by the input circuitry of the module. It also
indicates the input signal strength by changing in intensity as
the process changes from minimum to maximum.
If the LED fails to illuminate, or fails to change in intensity as
the process changes, check the module power or signal input
wiring. Note that it may be difficult to see the LEDs under bright
lighting conditions.
The red output LED provides a visual indication that the output
signal is functioning. It becomes brighter as the input and the
corresponding output change from minimum to maximum.
For current outputs, the red LED will only light if the output loop
current path is complete. For either current or voltage outputs,
failure to illuminate or a failure to change in intensity as the
process changes may indicate a problem with the module power
or signal output wiring.
Diagnostic Voltage Measurements
Using a meter with at least 10 megaohm input impedance, measure the voltage coming from the strain gauge at the locations shown.
Sensitivity is measured in mV/V.
Positive
Meter Lead
Negative
Meter Lead
Meter Reading
No pressure/load
Meter Reading
Full pressure/load
+ Exc.
– Exc.
Excitation Voltage
Excitation Voltage
+ Sig.
– Exc.
+ ½ Excitation Voltage
½ Excitation V (½ x Excitation Voltage x Sensitivity)
– Sig.
– Exc.
+ ½ Excitation Voltage
½ Excitation Voltage – (½ x Excitation Voltage x Sensitivity)
+ Sig.
– Sig.
Zero Volts
Excitation Voltage x Sensitivity
14
13
15
16
13 Power AC or DC
+
14
Earth Ground
16 Power AC or DC –
Module Power
Current sinking output
switch E set to “I”
External device provides
power to output loop
2
1
3
4
–
+
+
–
Loop
Power
Source
+
–
4-20 mA
Device
R
i
Current sourcing output
switch E set to “I”
+20 V at terminal 4
2
1
3
4
Passive
4-20 mA
Device
R
i
–
+20V
Voltage output
switch E set to “V”
2
1
3
4
Voltage
Device
–
+
Output Wiring
Calibration
The Zero, Span, and Excitation potentiometers are used to
calibrate the output.
Note: Perform the following calibration procedure any time
switch settings are changed.
This calibration procedure does not account for offsets or tare
weights. If your system has an offset, tare weight or deadweight,
refer to the "Using Offset Switch C" procedure.
To achieve optimum results, the system should be calibrated
using an accurate bridge simulator, pressure calibrator, or cali-
bration weights depending on the application.
1. Apply power to the module and allow a minimum 20 minute
warm up time.
2. Using an accurate voltmeter across terminals 10 and 12,
adjust the excitation voltage potentiometer for the exact volt-
age desired.
3. Provide an input to the module equal to zero or the minimum
input required for the application.
4. Using an accurate measurement device for the module
output, adjust the Zero potentiometer for the exact mini-
mum output signal desired. The Zero control should only be
adjusted when the input signal is at its minimum.
5. Set the input at maximum, and then adjust the Span pot for
the exact maximum output desired. The Span control should
only be adjusted when the input signal is at its maximum.
6. Repeat the zero and span calibration for maximum accuracy.
With Sense Leads
Sense
+
Sense –
Sense
+
Sense –
6
5
7
8
10
9
11 12
Strain
Gauge
V
0
+
V
0
–
V
EX
–
V
EX
+
Exc
+
Exc –
Sig
–
Sig
+
Sig
+
Exc –
Sig –
Exc
+
Test Cal.
Span
Zero
Test
Output
Input
DMD4059
Strain Gauge to DC
Isolated Transmitter
LED
Excitation
LED
OMEGA Engineering, Inc.
Sensor shield wire
(if equipped) should be
grounded at one end only
Sensor shield wire
(if equipped) should be
grounded at one end only
No Sense Leads
Jumper 6 to 12 ONLY if
sense leads are NOT used
6
5
7
8
10
9
11 12
Strain
Gauge
V
0
+
V
0
–
V
EX
–
V
EX
+
Exc
+
Exc –
Sig
–
Sig
+
Sig
+
Exc –
Sig –
Exc
+
Test Cal.
Span
Zero
Test
Output
Input
DMD4059
Strain Gauge to DC
Isolated Transmitter
LED
Excitation
LED
OMEGA Engineering, Inc.
1
2 3 4
5 6
7 8
9 10 11 12
13 14
15
16
Input
Cal. and Sense
Output
Power
To avoid damage
to the module,
do not make any
connections to
unused terminals
Wire terminal
torque
0.5 to 0.6 Nm or
4.4 to 5.3 in-lbs
Excitation Voltage Trim
Variable Brightness Output Indicator
Output Test Level Adjust
Push to Test Output
Output Span Calibration
Variable Brightness Input Indicator
Output Zero Calibration
