DMS-30DR-0-R-C datasheet(4/6 Pages) DELTA

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S U N L I G H T R E A D A B L E , A U T O - D I M M I N G L E D D I S P L A Y M E T E R S

DMS-30DR Series

S U N L I G H T R E A D A B L E , A U T O - D I M M I N G L E D D I S P L A Y M E T E R S

Figure 3. Differential Input Configuration

R1 + R2

x VIN = Reading

50k

Ω < R1 + R2 < 10MΩ

Figure 6. Floating Input Measurements

(Alternate Configuration)

Figure 5. Floating Input Measurements

Figure 4. Input Attenuation Circuit

RShunt = R1 = VFsr / IFsr

Where: VFsr = Full scale reading (in Volts)

IFsr = Relative full scale current (in Amps)

5. Process Control (4-to-20mA) Measurements:

In many common pro-

cess-control applications, a 4-to-20mA current loop is used to transmit

information. Because DMS-30DR meters have such high input imped-

ance, a simple shunt resistor across the meter's input can be used to

convert the loop current to a voltage. See Figure 7. The value of the

shunt resistor is a function of the scaling requirements of the particular

application and can be calculated using the following equation:

2. Differential Input Configurations:

Differential measurements can be

made with all DMS-30DR meters. Figure 3, though not a practical real-

world application, uses a voltage divider to demonstrate the concept

of a differential input signal. Be careful not to exceed the ±2V common

mode voltage limitation for 5V-powered meters.

3. Engineering Scaling:

For measuring voltages greater than the full

scale input range of a given meter, the input signal must be attenuated.

A simple voltage divider (similar to that shown in Figure 4) will scale

the input to within the range of the selected meter. R1 and R2 should

be precision, ±1%, metal-film resistors with absolute TCR's less than

50ppm/°C. See Ap Note 4 for more information on engineering scaling.

4. Floating Signal Source Measurements:

Floating signals can be

measured using the circuits shown in Figures 5 and 6. Connecting pin

10 (ANALOG COMMON) or pin 3 (5V RETURN) to (–) INPUT LO (pin

12) provides the reference point for the meter's input.

A "floating" input is a signal that has no galvanic connection to the

meter's power supply. In the figures below, the 1.5V battery illustrates a

true floating input.

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