Measurement Specialties CIO-SSH16 Adding Amplifiers Sample / Hold Chips, Range Calculation

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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

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Contents CIO-SSH16 Copyright 2000 Measurement Computing Corp Adding Amplifiers & Sample / Hold Chips This page is blank Introduction Software InstallationHardware Installation Power Cable Power Connector Signal CableGain Switches Analog Input Board SetupConnector Diagram Signal ConnectionAnalog Inputs Floating DifferentialExample DifferentialPage Amplification ArchitectureAnalog Input CIO-SSH16 vs. Programmable Gain A/D Boards Sample & Hold S15 S16 Droop Rate Sample and Hold Timing DiagramAdding Amplifiers Sample / Hold Chips Resolution CalculationRange Calculation Time to Sample CalculationAnalog input section SpecificationsSample / hold section Voltage Dividers Analog ElectronicsPage Differential & Single Ended Inputs Common Mode RangePage LOW Pass Filters Common MisunderstandingsGround Loops Converter # Volts A/D Resolution & Engineering UnitsCurrent Loop 4-20 mA Engineering UnitsSources of Noise NoiseSensor Noise Signal Wire NoiseSmoothing Data For your notes EC Declaration of Conformity