参数资料
型号: AB-161
英文描述: AB-161 - AN ERROR ANALYSIS OF THE ISO102 IN A SMALL SIGNAL MEASURING APPLICATION
中文描述: 抗体- 161 -一个错误分析在小信号测量中的应用ISO102
文件页数: 1/2页
文件大小: 28K
代理商: AB-161
SOME OBSERVATIONS
The total errors of the op amp and the iso amp combined are
approximately 0.6% of full-scale range. If the op amp had
not been used to preamplify the signal, the errors would have
been 74.4% of FSR. Clearly, the small cost of adding the op
amp buys a large performance improvement.
After gain and offset nulling, the dominant errors of the iso
amp are gain nonlinearity and power supply rejection. Thus,
well regulated supplies will reduce the errors even further.
The rms noise of the ISO102 with a 120Hz bandwidth is
only 0.18mVrms, which is only 0.0018% of the 10V full-
scale output. Therefore, even though the 16
μ
V/
Hz noise
spectral density specification may appear large compared to
other isolation amplifiers, it does not turn out to be a
significant error term. It is worth noting that even if the
bandwidth is increased to 10kHz, the noise of the iso amp
would only contribute 0.016% FSR error.
Mailing Address: PO Box 11400 Tucson, AZ 85734 Street Address: 6730 S. Tucson Blvd. Tucson, AZ 85706
Tel: (602) 746-1111 Twx: 910-952-111 Telex: 066-6491 FAX (602) 889-1510 Immediate Product Info: (800) 548-6132
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility
for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or
licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support
devices and/or systems.
FIGURE 1. 50mV Shunt Measures Current in A 500VDC Motor.
High accuracy measurements of low-level signals in the
presence of high isolation mode voltages can be difficult due
to the errors of the isolation amplifiers themselves.
This error analysis shows that when a low drift operational
amplifier is used to preamplify the low-level source signal,
a low cost, simple and accurate solution is possible.
In the circuit shown in Figure 1, a 50mV shunt is used to
measure the current in a 500VDC motor. The OPA27
amplifies the 50mV by 200X to 10V full scale. The output
of the OPA27 is fed to the input of the ISO102, which is a
unity-gain isolation amplifier. The 5k
and 1k
potentiom-
eters connected to the ISO102 are used to adjust the gain and
offset errors to zero as described in the ISO102 data sheet.
Input
Power Supply
V
OUT
23
4
14
15
Offset
21
1k
22
Offset Adjust
Reference
1
3
5k
10k
1
8
6
4
2
3
R
1
1k
2
R
F
200k
+15V
+V
CC1
7
–V
CC1
–15V
Offset
Adjust
V
IN
+
15V
24
1
–15V
0.1μF
0.1μF
+V
CC1
–V
CC1
+500VDC
+15V
–15V
9
16
10
–15V
+15V
13
12
0.1μF
0.1μF
+V
CC2
–V
CC2
Output
Power Supply
+15V
–15V
ISO102
C
0.022μF
C
0.04μF
Bandwidth
Control
V
D
Input Common
V
D
= 50mVDC (FS)
DC Motor
V
ISO
500VDC
Output Common
Gain
Adjust
Offset
Adjust
Gain Adjust
OPA27
AN ERROR ANALYSIS OF THE ISO102
IN A SMALL SIGNAL MEASURING APPLICATION
1994 Burr-Brown Corporation
AB-161
Printed in U.S.A. January, 1994
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