Copyright Keynes Controls Ltd 2005 - 2006

Part Number

Description

NPAI24-SC1-X-Y-Z

24 Bit Strain Gauge card
Const Current Excitation

NPAI16-SC1-X-Y-Z

24 Bit Strain Gauge card
Const Current Excitation

Sample
Rate

Noise
Peak-Peak

Noise
RMS

1

0.65 mStrain

0.14 uStrain

10

0.53 mStrain

0.09 uStrain

100

0.73 mStrain

0.15 uStrain

1KHz

1.72 mStrain

0.35 uStrain

Accuracy in measurement over a wide temperature range is a crucial factor in temperature measurements. The Keynes Controls Strain gauge interfaces are unequaled in performance. Stability over long periods of continued use makes them unmatched in reliability.

The Strain Gauge interface cards can be supplied to User Defined current excitation levels upon request in order to suit any manufacturers gauge requirements.

View looking into card

1

2

3

4

1 Isink
2 -Vin
3 +Vin
4 5V

Constant Current Excitation
24 bit & 16 Bit ADC Resolution Options
Individual ADC/card
Strain Gauge Sensor Support For - 120,350,500 & 1KW
Supports Full, ½ and ¼ bridge gauges
Sigma Delta ADC Conversion
Inbuilt Signal Conditioning
Simultaneous Sampling
1000V DC Opto-Isolation (Higher levels upon request)

The NetPod 4000 series instruments can be used for high precision strain readings when fitted with a range of strain gauge cards. Optional interfaces are available supporting both 24 bit and 16 bit ADC resolution converters offering the optimum in high resolution, high dynamic range and low noise measurements. The strain gauge interface can be used along side any other sensor input card when creating general purpose instrumentation solutions.

Bridge zeroing is undertaken as a software operation allowing the maximum user flexibility for its configuration. However for static measurements a bridge offset can be assigned that can manually zero the gauge signal response in order to examine drift over time.

The highest precision measurements are made using the full bridge strain gauges and when operating with the constant current sensor excitation the sensor cabling effects are removed from the readings. Any of the strain gauge configurations can be deployed a substantial distance away from the interface card without degrading any measurements.

1KW

1KW

+

-

Const Current

277 mA

G = Instrumentation
Amplifier

2

5V Supply

Strain
Gauge

Gauge-2

X = Bridge Type where 1 = Full Bridge
2 = Half Pridge
4 = ¼ Bridge

Y = Gain Setting = 1,10,100

Z = Excitation Current - (15 mA maximum)

Typical Noise Figures for 350 Ohm Gauge

Specifications

Table 1

ADC Resolution

Options for 24 & 16 Bit Sig Delta

Analogue Conversion

CMMR

160 d B

Current Source Drive Current

8.33 mA excitation Current gauges > 350 Ohm
To 15 mA excitation Current 120 Ohm gauge

Drift

10.0 ppm/°C

Sensor Interface

Full, ½ and ¼ gauge 120,350,500, 1kW

Measurement Range

+/- 10000 mStrain - Default
+/- 50,000 mStrain upon request

Operating Temperature

-20 to 60 Deg C

Short Circuit Current Limit

15 mA max

sample Rate

1- 1KHz/channel

Isolation

1000V DC Standard

3000V DC upon request

Dynamic Response

Sinc Filter

Load Regulation

< 0.005%

Bridge Balancing

Software

Gauge Factor

Typically 0-10 User Defined parameter

Sensor Offset

Set in mVolts - used to zero bridge
User defined value

Linearity

± 0.05 worst case

Figure 2 shows how a full bridge strain gauge
is connected to the Interface Cards

To download this data sheet as PDF