DMS-40PC PDF VIEW DOWNLOAD, DMS-40PC 데이터시트 - DATEL Data Acquisition products DatsheetQ

DMS-40PC 데이터 시트보기 (PDF) - DATEL Data Acquisition products

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DMS-40PC

4½ Digit, LED Display Precision, Miniature Digital Panel Voltmeters

DATEL Data Acquisition products

DMS-40PC Datasheet PDF : 6 Pages

1 2 3 4 5 6

DMS-40PC

4½ 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

Applications

2. Differential Input Configurations: Differential inputs can also

be measured with DMS-40PC meters as shown in the circuit of

Figure 3. Differential inputs must also originate from power

supplies that have a common ground with the meter's 5V

RETURN (pin 3). However, differential inputs usually have both

terminals above and/or below 5V RETURN. Figure 3, though not

necessarily a typical real-world application, does serve the

purpose of illustrating the concept of a differential signal.

The voltages developed across R1, R2 and R3 are equal to each

other and measure approximately +1.6666Vdc or 1/3 of the +5V

power source. More importantly, while the signal across R3 is

single-ended, both ends of R1 and R2 are well above ground

and are described here as being differential. Please note that

while the DMS-40PC can measure the voltages across either R2

or R3, it cannot measure the +1.6666 volts across R1! The

voltage at the lower end of R1 is approximately 3.333V and this

exceeds the common mode voltage limit of ±2V.

D M S -4 0 P C -1 -G S

DP1

(+ ) IN H I

( ) IN L O

+5V S U P

5V R E T

8 5 -2 6 4 V a c

D A TEL

D M S -P S 1 -C M

A C to D C C o n v e rte r

Figure 3. Differential Input Configuration

3. Power Supply Monitoring: One of the most widely used digital

panel voltmeter applications is monitoring the output voltage of a

system power supply — often the same supply that also powers

the meter. The low-power, red LED DMS-40PC-2-RL, with its

excellent 0.001Vdc resolution, can be configured to monitor

power supplies with outputs in the range of 4.5-18Vdc. The

circuit in Figure 4 uses a low-drop-out, three-terminal regulator

(LM-2931T-5, in a T0-220 package, available from National

Semiconductor) to provide regulated 5V power to the meter.

The LM-2931 was chosen because it has the following on-chip

protection features: reverse polarity, short circuit and thermal

runaway. The DMS-40PC-3-RL can monitor voltages up to

±200Vdc, provided a separate +5V power source is used since

many three-terminal regulators cannot operate with supply

voltages greater than 24V. Red, low-power LED models, with

their very low self-heating, are recommended for applications in

which low calibration drift is desirable. When using other, higher-

power, DMS-40PC models in combination with three-terminal

regulators, be sure to consult the regulator manufacturer's data

sheet to ensure the device is being utilized safely and correctly.

LM2931T-5

4.5 - 18Vdc

–

IN OUT

GND

22µF

10V

(+) IN HI

+5V SUP

5V RET

DMS-40PC-2-RL

DP2

(–) IN LO

Figure 4. 4.5-18V Power Supply Monitor

4. Floating Signal Source Measurements: A floating input is a

signal that, before it is applied to the DMS-40PC's inputs, has no

galvanic connection (direct current path) to the meter or the

meter's power supply. The circuit shown in Figure 5 illustrates

the necessary connections for measuring floating inputs. The

1.5V battery represents a true floating input signal since it

initially has no connection whatsoever in common with the

meter. Real-world floating inputs typically originate from power

supplies which are transformer isolated from the DMS-40PC’s

+5V supply.

The connection of pin 12 ((–) INPUT LO) to pin 10 (ANALOG

COMMON) is required in order to provide a bias return for the

meter’s input amplifier. This is because neither pin 11 nor pin 12

are tied to any reference voltage inside the DMS-40PC (see

Figure 1). These connections are not made internally in order to

give the meter the ability to make differential measurements as

described in a previous section.

1 .5 V

C E LL