A&D AS2503, Instruction Manual

Page: 59 / 90

４－１３
Care must be taken concerning the following points for connection to a data recorder.
(1) Where direct connections can be made
If a data recorder is capable of accepting a signal of more than 20 V
ｐ
-
ｐ
(+/-10V), it can be
directly connected to the amplifier unit.
(2) Where a voltage divider is required
If the input level of a data recorder is +/-1 V, a voltage divider is required. Pay due care to
the impedance.
In general, since the output impedance increases as the frequency band becomes higher, it
is expressed as:
Ｒ
0
（

）
+
Ｌ
0
（

H
）
.
If a voltage divider is inserted as shown in Fig. 4.7, this will cause errors, as described in the
following example.
Example:
Errors will be caused as shown in Table 4.7, if the voltage dividing ratio is 1/10 under the
following conditions:
Input impedance of data recorder:
Ｒｉ
=100
ｋ

,
Ｃｉ
=100
ｐＦ
Output impedance of the amplifier unit:
Ｒ
0
=
１

,
Ｌ
0
=200

Ｈ
R
1
(kΩ)
R
2
(kΩ)
Errors caused by voltage divider (5)
DC 1kHz 2kHz 5kHz 10kHz
90 11.1 -0.08 -0.08 -0.09 -0.12 -0.24
9 1.01 -0.02 0.02 -0.02 -0.02 -0.02
Table 4-7 Error Caused by Voltage Divider
4.4 How to Read Measured Values
This section describes how to read the measured values of a waveform recorded on a data
acquisition device or recorder.
Figure 4-10
CAL value
a
Ａ
B
b
Waveform
Measurement