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DMS-EB2

Multi-Purpose Application Board

for DMS-20PC/LCD Meters

MPM_DMS-EB2.E01 Page 2 of 4

TECHNICAL NOTES

APPLICATIONS

1.LCD Backlighting: To backlight a DMS-20LCD meter, connect J1, pin 3

(TEST/HOLD IN) to J1, pin 6 (GND). This allows for external control,

via a switch, of the backlight feature. The switch should be rated for low

voltage operation at 35mA.

2.9V LCD Meters: DMS-20LCD-X-9 meters cannot be used in a single-

ended configuration, i.e., with (–) IN LO tied to GND. On these models,

both (–) IN LO and (+) IN HI have to be a minimum of 1.5V above and

1.5V below J1 pins 6 and 5, respectively. To operate from a 9V or 12V

battery with (–) IN LO tied to GND, use a 5V-powered meter (DMS-

20LCD-X-5), install U1 (LM7805CT) and open SG4.

3. Input Resistor Dividers: Always use 1%, or better, metal-film resistors

for R1 and R2, and also make sure their power and voltage ratings are

adequate for the given application.

4. Using U1 (LM7805CT): The input power range specified in the Battery

Operation section is rated conservatively assuming a 100mA LED meter

or a 35mA backlit LCD meter. If a non-backlit LCD model or the low-

power LED model is used, the input voltage range can be extended up to

32Vdc.

As shipped, the DMS-EB2 is configured for single-ended operation.

This configuration is preferred for simple voltage measurements and will

generally cover most standard applications. Figure 1 indicates which

solder gaps are shipped closed from the factory.

Simply solder the board onto the meter (pin 1 to pin 1), connect

the power supply to J1, pin 5 (+V) and the power return to J1, pin 6

(GROUND).

1.Decimal Point Placement: DATEL ships the DMS-EB2 with all decimal

point solder gaps (SG1, SG2 and SG3) open. To enable a specific

decimal point, close its respective solder gap with solder. When

re-assigning decimal places for subsequent applications, remember to

unsolder previously closed solder gaps.

Close SG1 for 1.999 (DP1)

Close SG2 for 19.99 (DP2)

Close SG3 for 199.9 (DP3)

2. Display Test (Not Available on LCD Models): Tie pin 4 (TEST/HOLD

OUT) to pin 3 (TEST/HOLD IN) to test the display of the DMS-20PC.

Do not leave the meter in the test mode for more than 10 seconds. On

LED meters with the HOLD option, tying pins 3 and 4 together freezes

the display reading.

3. Battery Operation: Open SG4 and install U1 (LM7805CT) with its metal

tab facing to the left as shown in Figure 3. Allowable input power ranges

(J1, pins 5 and 6) are as follows:

DMS-20PC-X-XS +7.5 to +12.6Vdc

DMS-20PC-X-XL

+7.5 to +32Vdc

C2 (10μF/35V) can be added to reduce noise. Observe correct polarity.

Refer to Technical Note 4 for more information.

Figure 2. J1 Connector Pinout

Pin

Function

1 (+) INPUT HI

2 (–) INPUT LO

3 TEST/HOLD IN

4 TEST/HOLD OUT

5 +V (Positive power connection)

6 –V (Ground, negative power return)

12

34

56

J1

DMS-EB2

Application board with mating connector and terminals

DMS-BZL3

DMS-20 bezel assembly

DMS-BZL4

DMS-20 bezel assembly with sealing gasket

39-0304000

LM7805CT (U1), +5V-output, three-terminal regulator

39-2359625

6-position pc-board socket

Input Supply Range

See applicable meter's data sheet

Input Supply Range U1 (LM7805CT) Installed:

DMS-20PC-X-XS

+7.5 to +12.6V

DMS-20PC-X-XL

+7.5 to +32.0V

DMS-20LCD-X-5

+7.5 to +32.0V

DMS-20LCD-X-5B

+7.5 to +12.6V

Operating and Storage Temperature

See applicable meter's data sheet

Humidity

0 to 95%, non-condensing

Dimensions

1.25" (31.8mm)L x 0.75" (19.1mm)H

J1 Connector & Wire Information

Terminal Type

DATEL P/N 39-2099090

Crimp Tool

DATEL P/N 39-2099000

Wire Size

22 to 26 AWG

Insulation Diameter

0.062" (1.57mm) max.

Stripping Length

0.100" to 0.125"

(2.54 to 3.17mm)

Ordering Information

A 10μF/35V tantalum capacitor (C2 on schematic) should be installed

with the polarized end next to the + symbol on the DMS-EB2. This is

especially important if the power source is located far from U1.

5. Soldering: DATEL recommends the use of "no-clean" solders when

making modifications to the DMS-EB2.