DMS-20PC データシートの表示（PDF） - DATEL Data Acquisition products

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DMS-20PC

3½ Digit, LED Display Low-Cost, Subminiature Digital Panel Voltmeters

DATEL Data Acquisition products  

3½ D I G I T, L E D D I S P L AY D I G I TA L PA N E L V O LT M E T E R S

DMS-20PC

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 9 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.

8. Suggested Mating Connectors:

Panel mounted:

Connector housing

Terminal type

Crimping tool

Wire size

Insulation diameter

Stripping length

MOLEX P/N 22-01-2061

MOLEX P/N 08-65-0805

MOLEX P/N 11-01-0037

22 to 26 AWG

0.062" (1.57mm) maximum

0.100 to 0.125" (2.54 to 3.17mm)

Board mounted:

Socket

SAMTEC P/N SSW-106-02-T-S

Applications

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 909kΩ 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).

+

VIN

–

120 VAC

11

(+) IN HI

12

(–) IN LO

1

+5V SUP

DATEL

UPA-5/500

DMS-20PC-1

8

REF OUT

2

DISPLAY

ENABLE

6

DP1

7

REF IN

3

5V RET

AC to DC Converter

Figure 2. Single-Ended Input Configuration

3

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