DMS-20PC-2OS datasheet(3/6 Pages) ETC

3 / 6 page

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DIGIT ,

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DIGIT AL

P ANEL V O L TMETERS

DMS-20PC

Applications

Figure 2. Single-Ended Input Configuration

8. Suggested Mating Connectors:

Panel mounted:

Connector housing

DATEL P/N 39-2079400

Terminal type

DATEL P/N 39-2099090

Crimping tool

DATEL P/N 39-2099000

Wire size

22 to 26 AWG

Insulation diameter

0.062" (1.57mm) maximum

Stripping length

0.100 to 0.125" (2.54 to 3.17mm)

Board mounted:

Socket

DATEL P/N 39-2359625

DMS-20PC meters are highly versatile devices that can be used in

hundreds of applications. The application circuits chosen for this

section are ones that have historically received many inquiries.

The schematic in Figure 1 shows that the meter's high-impedance

input consists of an op amp powered from a ±5Vdc power supply

(the –5V is internally generated). One can easily see why input

signals applied to (–) INPUT LO and (+) INPUT HI have to be kept

within the power supply rails of ±5V. Also note that only pin 11 has a

current-limiting 909k

Ω series resistor. High input voltages that have

a common ground with pin 3 (5V RETURN) should only be applied

to pin 11 ((+) INPUT HI) and never to pin 12. In these high-voltage

cases, pin 12 should always be tied to pin 3 (5V RETURN).

The schematic also shows that pin 3 is the meter's zero-volt

reference point — regardless of the type of power or signal source

used. This is an important point to keep in mind when a digital or

analog multimeter is used to make system measurements. The

multimeter's negative lead (usually the black one) must be

connected to pin 3 (5V RETURN).

1. Single-Ended Input Configurations: True single-ended

measurements can be made with any DMS-20PC meter. The

circuit of Figure 2 avoids problems normally associated with

ground-loop currents. Separate ground runs should be used

for 5V RETURN (pin 3) and (–) INPUT LO (pin 12).

4. DISPLAY TEST/HOLD (Pin 9) Function: Pin 9 is a dual-function

pin. On all standard models (without "-H" suffix), tying pin 9 to pin

1 (+5V SUPPLY) activates the meter's DISPLAY TEST feature.

All display segments, except the decimal points, will be

illuminated. The display will show "1888" ("–1888" if a negative

input signal is present). Do not leave the meter in the test

mode for more than 10 seconds as this will cause the

meter's operating temperature to rise and possibly affect its

performance. Pin 9 must be left open when the test function is

not being used.

On models with the "-H" suffix (DMS-20PC-1-RS-H for example),

pin 9 serves as a DISPLAY HOLD control pin. Tying pin 9 to +5V

SUPPLY (pin 1) on these models will hold or "freeze" the current

display reading indefinitely. Pin 9 must also be left open when the

hold function is not being used. After disabling DISPLAY HOLD,

allow the meter a full 10 seconds to resume normal calibrated

operation before holding a new reading.

The DISPLAY TEST or DISPLAY HOLD pin should normally be

connected, via a selector switch, to pin 1 (+5V SUPPLY). If

automatic, logic-controlled operation is desired, only PNP or

MOSFET transistors should be used. The base or gate of these

transistors should be driven sufficiently hard to bring pin 9 within

0.05V of +5V SUPPLY.

5. DISPLAY ENABLE (Pin 2) Function: On all models, tying pin 2

to pin 1 (+5V SUPPLY) applies full power to the LED display. This

is the normal mode of operating the meter. Leaving DISPLAY

ENABLE open (no connection), only turns off the LED display.

The meter's analog-to-digital converter continues to sample the

input signal. Total current consumption with the display off is

approximately 400µA (0.4mA). This is a very useful feature if the

meter is used in battery-powered equipment.

With the exception of the low-power red LED models (DMS-

20PC-X-RL), a regulated voltage lower than +5V SUPPLY can be

used to dim the display intensity. Display intensity control is best

performed with the high brightness, red LED, DMS-20PC-X-RH

model. All low-power red LED models must have DISPLAY

ENABLE tied directly to pin 1 (+5V SUPPLY). Voltages applied to

DISPLAY ENABLE must never be greater than +5V SUPPLY.

6. Gain Adjust: There is a gain-adjust potentiometer on the back

of each meter. It has approximately ±50 counts (±2.5%) range of

adjustment. Since these devices essentially have no zero/offset

errors, a gain adjustment is effectively an overall accuracy

adjustment. Though they may be performed at any point (except

zero), accuracy adjustments are most effective when performed

with higher level input signals. The circuit shown in Figure 10

provides ±10% range of adjustment.

7. Soldering Methods: All models in the DMS-20PC Series easily

withstand most common wave soldering operations. We

recommend, however, that you evaluate the effects your

particular soldering techniques may have on the meter’s plastic

case and high-precision electrical performance. We recommend

the use of water-soluble solders and thorough cleaning

procedures.

+5V SUP

(–) IN LO

5V RET

DATEL

UPA-5/500

120 VAC

(+) IN HI

DP1

–

AC to DC Converter

VIN

DMS-20PC-1

REF OUT

REF IN

DISPLAY

ENABLE

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