Features

••••• Displays true rms values of ac inputs

••••• ±0.5% accuracy for DMS-30PC-0

or DMS-30LCD-0-5

••••• ±2% accuracy for DMS-30PC-1

or DMS-30LCD-1-5

••••• Also works with DMS-40PC/LCD meters

(see Ap Note 11)

AC-to-RMS Converter

Application Board for

DMS-30PC/LCD Meters

DMS-EB-RMS

Ordering Information

DMS-EB-RMS

AC-to-RMS conversion

board

DMS-BZL1

Bezel assembly

DMS-BZL2

Bezel assembly with

sealing gasket

Functional Specifications

Vac Measurement Range:

±200mV meters

0 to 199.9Vac

±2V meters

0 to 750Vac

Conversion Accuracy:

0-200Vac

±0.5%

0-750Vac

±2%

Crest Factors

3, maximum

Input Frequency Range

40Hz to 2kHz

Primary Operating Power

+5V (±5%)

Current Consumption (Board only)

+0.5mA typ., +1mA max.

Operating Temperature Range

0 to +60°C

Storage Temperature Range

–20 to +75°C

Humidity

0 to 95%, non-condensing

Dimensions

2.02" (51.31mm)W x 0.83" (21.08mm)H

Figure 1. DMS-EB-RMS Schematic Diagram

Actual Size

DS-0398A

1/98

Technical Notes

Description: The DMS-EB-RMS board allows the true rms value of ac signals to be displayed

on 5V-powered DMS-30PC/LCD digital voltmeters.The meter/board combination has an input

range of 0-750Vac with ±2V meters (1Vac resolution) or 0-199.9Vac with ±200mV meters

(0.1Vac resolution). A built-in screw-terminal block reliably interfaces signal and power

connections.The DMS-EB-RMS now accommodates user-installed modifications such as

input-scaling resistors and isolated +5V dc/dc converters.

Power and Safety Precautions: The DMS-EB-RMS’s AC HI and AC LOW inputs are not

electrically isolated from its 5V supply (AC LOW is connected directly to 5V RETURN).

When measuring any input signal which is derived from ac power mains, a dedicated (i.e.,

it only powers the DMS-EB-RMS), transformer-isolated +5V supply, with a minimum 1kV

breakdown rating, must be used to power the DMS-EB-RMS board/meter combination.

When measuring ac power mains inputs, never connect the DMS-EB-RMS’s 5V RETURN

to chassis/earth ground anywhere in the system. Failing to follow these instructions could

defeat any safety grounding and will place the system +5V power supply, and all its

associated circuitry, at dangerously elevated ac-line potentials. In many applications, the

DMS-EB-RMS installation is required to meet

electrical code requirements. To ensure

safe operation, the DMS-EB-RMS board

should only be installed and serviced by

technically-qualified personnel. See DMS

Application Note 11 for more details.

(–) INPUT LO

(+) INPUT HI

REF. OUT

REF. IN

1

56

3

+5V

5V Return

TB1

CAV

OUT

COM

CF

CC

LV

OSC

V+

CAP–

GND

CAP+

BOOST

SG1

SG2

SG3

5V RETURN

DP3

DP2

DP1

+5V SUPPLY

C5

2.2µF

+

+

R1

988k

R2

988k

R3

1.98k

+

C2

10µF

C1 100µF

+

1

2

3

4

5

6

7

8

5

6

7

8

1

2

3

4

U1

U2

AC HI

3

4

5

6

1

2

SG4

J1

12

11

8

7

10

9

JP1

J6

GND 2

1

3

U3

Q

PS1

Q

1

2

3

4

C4

2.2µF

J4

J5

AC LOW

Components are user-supplied

and not part of the standard product.

DC/DC

–V

+V

Q

®®

DATEL, Inc., Mansfield, MA 02048 (USA)

• Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356 • Email:sales@datel.com • Internet: www.datel.com

DATEL makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained

herein do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without notice. The DATEL logo is a registered DATEL, Inc. trademark.

R1

R2

R3

U2

12

1

C4

1

SG 4

SG 3

U1

PS1

J1

U3

JP 1

J6

2

C2

C1

C5

J4

TB 1

J5

J2

J3

1

23

4

5

6

11

10

9

8

7

Purchase on-line at www.datel.com