Martel Electronics SP300 - Manual (Page 4)

Specifications liable to change without prior warning SP 300 Issue 3 October/2001 M.C. Applies to SP 300/1
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.
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SCALING
Two 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
200V 1M** 1k
2000V* 1M** 100R
200 A 0R 1k
2mA 0R 100R
20mA 0R 10R
200mA 0R 1R
µ
Voltage
Current
Page 4 of 4
* Ensure that Ra is rated for high voltage use.
** Ensure solder link LA is cut.
SP 300
3½ Digit LED Voltmeter Module
IH
IL
0V
0V
+
-
±200mV
V+
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.
IH
IL
COM
0V
0V
+
-
±200mV
V+
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.
V+
V+
5k
Set Zero
220k
R
IH
IL
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
COM
IH
+5V
Load
Shunt
R
L
V+
V
A
S
1
IL
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
IH
IL
COM
0V
0V
R
V+
V+
Measuring current.
The meter's supply is isolated
from the current being measured.
R = 0.2
I
FSR
+
-
Ra
Rb
IH
Vin or in I
IL
SP 300
LA
www.lascarelectronics.com
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PO Box 770, Londonderry, NH 03053 1-800-821-0023
www.martelcorp.com