Meilhaus Electronic redlab 1208fs, Руководство пользователя

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RedLab 1208FS User's Guide Functional Details
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ƒ The wire carrying the reference signal connects to CH0 IN LO, CH1 IN LO, CH2 IN LO, or
CH3 IN LO.
ƒ The third wire connects to GND.
A low-noise precision programmable gain amplifier (PGA) is available on differential channels to provide gains
of up to 20 and a dynamic range of up to 12-bits. Differential mode input voltage ranges are ±20 V, ±10 V,
±5 V, ±4 V, ±2.5 V, ±2.0 V, ±1.25 V, and ±1.0 V.
In differential mode, the following two requirements must be met for linear operation:
ƒ Any analog input must remain in the − 10V to +20V range with respect to ground at all times.
ƒ The maximum differential voltage on any given analog input pair must remain within the selected voltage
range.
The input [ common - mode voltage + signal ] of the differential channel must be in the − 10 V to +20 V range in
order to yield a useful result. For example, you input a 4 V pp sine wave to CHHI, and apply the same sine
wave 180° out of phase to CHLO. The common mode voltage is 0 V. The differential input voltage swings from
4 V
- (-4 V) = 8 V to -4 V - 4 V = -8V. Both inputs satisfy the -10 V to +20 V input range requirement, and the
differential voltage is suited for the ±10 V input range (see Figure 6).
+4V
-4V
+4V
-4V
0V
CHLO
CHHI
+/-8V
8V Differential
Measured Signal
Figure 6. Differential voltage example: common mode voltage of 0 V
If you increase the common mode voltage to 11 V, the differential remains at ±8 V. Although the [ common -
mode voltage + signal ] on each input now has a range of +7 V to +15 V, both inputs still satisfy the -10 V to
+20 V input requirement (see Figure 7).
+11V
+7V
+11V
+/-8V
+15V
8V Differential
CHLO
CHHI
Measured Signal
Figure 7. Differential voltage example: common mode voltage of 11 V