鈥?/div>
Also works with DMS-40PC/LCD meters
(see Ap Note 11)
AC-to-RMS Converter
Application Board for
DMS-30PC/LCD Meters
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 鹵2V meters (1Vac resolution) or 0-199.9Vac with 鹵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鈥檚 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鈥檚 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
P S 1
J 1
R 3
J 6
R 2
J 2
1
1 2
safe operation, the DMS-EB-RMS board
2
U 1
1 1
J P 1
should only be installed and serviced by
U 3
1 0
R 1
J 5
J 3
J 4
technically-qualified personnel.
See DMS
C 1
T B 1
9
C 5
1
Application Note 11 for more details.
8
C 4
7
S G 4
Functional Specifications
(T
A
= +25擄C, V
CC
= +5V)
Vac Measurement Range:
鹵200mV meters
0 to 199.9Vac
鹵2V meters
0 to 750Vac
Conversion Accuracy:
0-200Vac
鹵0.5%
0-750Vac
鹵2%
Crest Factors
3, maximum
Input Frequency Range
40Hz to 2kHz
Primary Operating Power
+5V (鹵5%)
U 2
C 2
1
2
3
4
5
6
S G 3
C1 100碌F
+
5
Current Consumption (Board only)
+0.5mA typ., +1mA max.
Operating Temperature Range
0 to +60擄C
Storage Temperature Range
鈥?0 to +75擄C
Humidity
0 to 95%, non-condensing
Dimensions
2.02" (51.31mm)W x 0.83" (21.08mm)H
CAV
OUT
鈥揤
S
4
3
2
1
5
6
7
8
V
OUT
CAP鈥?/div>
GND
4
3
2
1
C5
2.2碌F
(鈥? INPUT LO
12
6
7
CF
LV
1
+5V SUPPLY
U1
+V
S
V
IN
U2
OSC
V+
CAP+
BOOST
+
(+) INPUT HI
11
8
COM
CC
2
10
J1
+
9
SG4
REF. OUT
8
R1
988k
R2
988k
C2
10碌F
C4
2.2碌F
3
5V RETURN
+
SG1
4
DP3
SG2
5
DP2
R3
1.98k
SG3
REF. IN
7
6
DP1
JP1
J4
J5
U3Q
1 V
IN
3
V
OUT
GND 2
1
鈥揤
2
+V
PS1Q
+V
IN
DC/DC
鈥揤
OUT
3
4
Ordering Information
DMS-EB-RMS
DMS-BZL1
DMS-BZL2
AC-to-RMS conversion
board
Bezel assembly
Bezel assembly with
sealing gasket
TB1
J6
1
AC HI
3
AC LOW
5
+5V
6
5V Return
Q
Components are user-supplied
and not part of the standard product.
Figure 1. DMS-EB-RMS Schematic Diagram
DS-0398A
1/98
DATEL, Inc.,
Mansfield, MA 02048 (USA)
鈥?/div>
Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356
鈥?/div>
Email: sales@datel.com
鈥?/div>
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.
S G 2 S G 1
1
