ANDERS ELECTRONICS OEM335A Service Manual

digital panel modules user guide

OEM335A 3.5 digit LED voltmeter module

features

Bright, red LED display
Single 5V DC operation.

10.16mm digit height
Decimal point selectable
Self mountable.
Single ended or differential input.

DESCRIPTION

The OEM335A is a complete digital voltmeter module in a
very compact package incorporating a dual-slope
analogue to digital converter, a 100mV reference with
200mV full scale input sensitivity.
The large sized LED makes the module easily readable
from distance away. Auto-zeroing is provided by the
circuit itself, so no zero adjustment is required. The
module also has input polarity and over-range indication.

DIMENSIONS mm

ELECTRICAL CHARACTERISTICS TA=25OC

CHARACTERISTIC MIN TYP MAX UNIT

Power supply Voltage 4.75 5 5.25 V

Power Supply Current 180 mA

Sampling Rate 2.5 Reading/sec.

Accuracy 0.1 ±1 % ± digits

Input Impedance 100 M

Input leakage Current 1 10 PA

Temperature Coefficient 100 PPM/

¡

Ω

o

C

PIN FUNCTIONS

PIN SYMBOL DESCRIPTION

1 V+ +5V Power supply.

2 GND Ground (0V for power supply).

3 IN HI Signal input terminals. If potential on INHI is

4 IN LO lower than INLO, display will show negative.

5DP1

6DP2

7DP3

8 DP.com Decimal point return

Decimal point select. The decimal point will be
shown if connected to DP.com and will be off if kept
floating.

PANEL CUT OUT

OPERATING SPECIFICATION

Operating voltage 5V DC + 5%

Operating temperature 0 to 50

Storage temperature -10 to 70

Relative humidity 80%

O

C

O

C

ORDERING INFORMATION MODULE VIEW FROM REAR

OEM335A 3.5 Digit, 200mV LCD voltmeter module

LM201 Connector and cable

OEM335AV4 Revision 4 - 21/10/03

USER INSTRUCTIONS CONNECTION DIAGRAM BASIC CONFIGURATION

The OEM335A is designed for +5V single rail supply.
Incorrect supply will damage the module.
Apply the input signal between pin 3 (INHI) and pin 4
(INLO). The input range is 0 - 199.9mV.
Over range is indicated by illuminating a "1" in the most
significant digit and blanking the other digits.
It is recommended to use this module with floating inputs
i.e. the low input signal (INLO) must be isolated from the
power supply ground (GND). Where (INLO) must be
referenced to the power supply, connect via a 10KΩ
resistor and a 0.1µF capacitor as shown opposite.
To activate a decimal point, connect the appropriate
decimal point pin to DPcom.

APPLICATION CIRCUITS

DC VOLTAGE MEASUREMENT

To measure voltages greater than 200mV
an attenuator is required.

R1+R2

IN=VD

V

EXAMPLES

VIN Display VD R1 R2

2V 1.999V 199.9mV

10V 1500rpm 150mV

The input impedance becomes R1+R2. Choose accurate stable
resistors. Typically, R1=1MΩ. 9MΩ is a practical upper limit.

x

VD max. is 199.99mV

R2

1MΩ 110KΩ

1MΩ 15KΩ

DC CURRENT MEASUREMENT

Vs

2

RS Ω

IN

S PS

1Ω

0.1Ω

I

IN

0.04W

Ω

0.4W

Shunt resistance RS =

It is important to note the power
dissipation in the shunt and choose
resistor rating accordingly

P

EXAMPLES

2

Vs

=

= I

S

I

IN

Current R

200mA

2A

MULTI-RANGE DC VOLTAGE MEASUREMENT

For multi-range, use, a 2 pole,
4 way rotary switch. 1 pole for
range select and the other to
connect the appropriate
decimal point to V+

DC MULTI-RANGE CURRENT MEASUREMENT

For multi-range, use, a 2 pole,
5 way rotary switch. 1 pole for
range select and the other to
connect the appropriate
decimal point to V+

AC VOLTAGE MEASUREMENT

The meter can only measure DC. Use the above circuit to convert AC to
DC. For voltages above 200mV AC, a potential divider is required before
the converter circuit as shown in the "Voltage measurement" section
above

anders

electronics plc Bayham Place, London NW1 OEU UK

Tel: [phone] Fax: [phone] www.anders.co.uk

OEM335AV4 Revision 4 - 21/10/03