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v1.02
05/06/30
10
ES51918
11,000 Counts Auto DMM
1.1.6 The true RMS-to-DC conversion with ES7R
If ES7R is used for true RMS-to-DC measurement, the test circuit is shown in Figure 3.
Make ADO and ADI pin short, and TEST5 pin keeps float. Connect OVSG pin to
AGND through a switch in ACV measurement mode. If the DCV and ACV
measurement modes are in the same rotary switch, please also add this switch in the
rotary switch. The configuration of this switch will not influence the precision of DCV
measurement. The 500kΩ VR, 1kΩ resistor and 10Ω resistor are used for external
offset trim. If users don’t want to use external offset trim, please remove these 3
resistors and connect pin1 of ES7R to pin8 of ES7R.
Figure 3. The true RMS-to-DC conversion with ES7R
+Vs
-Vs
500K
1K
100
AGND
OVSG
OR1
VR5
VR4
VR3
VR2
TEST5
ACVL
ACVH
1.111M
101K
10K
1K
99.5
AGND
ACV
AGND
1
2
3
4
8
7
6
5
2.2u
+
+Vs
AGND
-Vs
100K
1.5K
-Vs
N1
N2
AGND
+Vs -Vs
2
3
1
5
4
7
6
AGND
1u
+
47K
TL061
30K
10K
ADI
ADO
ADOHZ
PWD
OP-
OP+
OPO
AGND
10K
30K
0.1u
AGND
+Vs
+Vs
-Vs
4.7u
Note: The filter capacitors for +Vs
and -Vs are recommended to near to
the power terminals of ES7R and
external OPAMP.
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