Martel Electronics OEM1B-LED - Manual (Page 4)

Specifications liable to change without prior warning OEM 1B-LED Issue 2 September/2002 M.C. Applies to OEM 1B-LED/1
Page 4 of 4 Page 4 of 4
Page 4 of 4
EXTERNAL SCALING
Two external resistors Ra and
Rb may be used to alter the
full scale reading (FSR) of the
meter - see table. The meter
will have to be re-calibrated
by adjusting the calibration
potentiometer on the rear of
the module.
FSR Ra Rb
2V 910k 100k
20V 1M 10k
Vin 200V 1M 1k
2000V* 1M 100R
200 A 0R 1k
2mA 0R 100R
Iin 20mA 0R 10R
200mA 0R 1R
µ
Voltage
Current
+
-
Ra
Rb
IHI
Vin or in I
ILO
OEM 1B-LED
*Ensure that Ra is rated for high voltage use.
APPLICATIONS
Do not connect more than one meter to the same power supply if the meters cannot use the same signal
ground. Taking any input beyond the power supply rails will damage the meter.
www.lascarelectronics.com
OEM 1B-LED
3½ Digit LED Voltmeter Module
IHI
ILO
0V
0V
+
-
±200mV
V+
Measuring a single ended input
voltage referenced to supply, i.e. the
input voltage and the meter's power
supply share the same 0V rail.
IHI
ILO DP1
COM
0V
0V
+
-
±200mV
+4.75 to +5.25V +4.75 to +5.25V +4.75 to +5.25V
+4.75 to +5.25V
V+
Measuring an input voltage referenced
to a floating supply, i.e. the input
voltage and the meter's power supply
are isolated from each other.
Circuit shows DP1 enabled.
V+
5k
Set Zero
220k
R
IHI
ILO
COM
0V
0V
I +
I-
4-20mA
current loop
Measuring a 4-20mA loop current.
The meter's power supply must be
isolated from the 4-20mA current
loop.
R= Reading at 20mA
160
IHI
ILO
COM
0V
0V
R
V+
Measuring current.
The meter's supply is isolated
from the current being measured.
R = 0.2
I
FSR
2
1
3
4 9
5
2
1
3
4
5
2
1
3
4
5
2
1
3
4
COM
IHI
+5V
Load
Shunt
R
L
V+
V
A
S
1
ILO
0V
Rs
7805
220nF 470nF
10uF
V
supply
Measuring supply voltage and current to a load.
Rs = 200mV
Display DP1, DP2 or DP3, by connecting to 0V, as required.
S selects between voltage and current measurement.
Ra and Rb shown scaled for 200V
1
FSR
(e.g. 0.1 / 400mW for 2A full scale) Ω
I
FSR
I
Ra=1M
Rb=1k
2
1
3
4
5
PO Box 770, Londonderry, NH 03053 1-800-821-0023
www.martelcorp.com