Measurement-computing CIO-SSH16 Manuel d'utilisateur télécharger pdf (Page 17)

To calculate the effect of the droop rate on the accuracy of your measurement, the

range of the signal, the resolution of the A/D converter and the time between HOLD

and A/D acquisition are needed. Here is an example.

RANGE CALCULATION

Signal Range ±50 millivolts

Gain 100

Amplifier Output ±5 Volts At full scale

RESOLUTION CALCULATION

A/D resolution 12 bits 1 part in 4096

Volts per bit 2.44 millivolts 10/4096

TIME TO SAMPLE CALCULATION

Number of channels 8

Sample Rate 4,000 samples/ sec.

Time between samples 250 microseconds 1/4000

Time from HOLD to CH8 2 milliseconds 0.000250 * 8

DROOP CALCULATION

Maximum droop to CH8 ±0.0001V * 2 = ±2 microvolts.

Less than 8% of the value of 1 bit.

It is clear from this calculation that droop rate is not a problem even at low sampling

rates. The sample rate would have to drop to less than 400 samples/ sec. over eight

channels before the droop was detectable by a 12 bit A/D converter.

4.6 ADDING AMPLIFIERS &

SAMPLE / HOLD CHIPS

The CIO-SSH16 comes standard with

four amplifiers and three sample & hold

chips installed.

To add an additional channel, order the

two chip set, CIO-SSH-AMP shown

here. Twelve CIO-SSH-AMP chip sets

may be added for a total of 16 channels

(Figure 4-8). You can acquire LF398

S&H and INA110 amps on your own

and install them if you wish without

voiding your warranty.

Figure 4-8. CIO-SSH-AMP Chip Set

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 31 32

Pas de commentaire

Measurement-computing CIO-SSH16 Manuel d'utilisateur Page 17