Copyright Keynes Controls Ltd 2005 - 2006

Part Number

Description

NPAI24-RTDA

24 Bit RTD Type A

NPAI24-RTDB

24 Bit RTD Type B

NPAI16-RTDA

16 Bit RTD Type A

NPAI16-RTDB

16 Bit RTD Type B

Sample
Rate

Noise
Peak-Peak

Noise
RMS

1

0.0227 °C

0.0027 °C

10

0.0377 °C

0.0060 °C

100

0.0980 °C

0.0112 °C

1KHz

0.2919 °C

0.0414 °C

Figure 2 shows the 4 Wire RTD Sensor Connection to the Interface Cards

Specifications

ADC Resolution

Options for 24 & 16 Bit Sig Delta

Analogue Conversion

CMMR

160 d B

Current Source Drive Current

5V voltage with 277 uA
excitation current

Drift

10.0 ppm/°C

Sensor Interface

4 & 3 wire RTD (PT100)

Measurement Range

- 200 to + 600 Deg C (Standard)
-200 to + 800 Deg C (Optional)

Operating Temperature

-20 to 60 Deg C

Short Circuit Current Limit

277 uA max

sample Rate

1- 1KHz/channel

Isolation

1000V DC Standard

3000V DC upon request

Dynamic Response

Sinc Filter

Load Regulation

< 0.005%

Linearity

± 0.05 worst case

Typical Noise Figures - PT100 Sensor

Accuracy in measurement over a wide temperature range is a crucial factor in temperature measurements. The Keynes Controls RTD interfaces are unequaled in performance. Stability over long periods of continued use makes them unmatched in reliability. Precision construction make them highly interchangeable for easy replacement without need for re-calibration.

PLATINUM RESISTANCE ELEMENTS
DEVIATION FROM CALIBRATION VALUES

°C

°F

Ohms

°C

°F

°C

°F

Ohms

°C

°F

-200

-328

± 0.56

± 1.3

± 2.34

400

752

± 0.79

± 2.3

± 4.14

-100

-148

± 0.32

± 0.8

± 1.44

500

932

± 0.93

± 2.8

± 5.04

0

32

± 0.12

± 0.3

± 0.54

600

1112

± 1.06

± 3.3

± 5.94

100

212

± 0.30

± 0.8

± 1.44

700

1292

± 1.17

± 3.86

± 6.84

200

392

± 0.48

± 1.3

± 2.34

800

1472

± 1.28

± 4.3

± 7.74

300

572

± 0.64

± 1.8

± 3.24

850

1562

± 1.34

± 4.6

± 8.28

Table 1

Table 2

Table 2 shows the deviation from the results expected by the use of the PT100 resistive temperature detector for general purpose temperature measurements.

View looking into card

1

2

3

4

1 Isink
2 -Vin
3 +Vin
4 5V

20KW

20KW

+

-

Const Current

277 mA

8R2W

G = Instrumentation
Amplifier

4

3

2

1

PT100

5V Supply

Constant Current Excitation
277 mA Drive Current - Minimised Sensor Self Heating
24 bit & 16 Bit ADC Resolution Options
Individual ADC/card
4 Wire RTD Sensor Support - PT100
-200 to 800 Deg °C Measurement Range
Sigma Delta ADC Conversion
Inbuilt Signal Conditioning
1000V DC Opto-Isolation (Higher levels upon request)

The NetPod 4000 series instruments can be used for high precision temperature readings when fitted with a range of RTD sensor interface 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 RTD interface can be used along side any other sensor input card when creating general purpose instrumentation solutions.

All of the ranges of RTD interface cards support direct connection to the 4 wire sensors and Figure 2 shows how for a 4 wire sensor connection is made to the interface.

High precision measurements are made using the 4 wire PT100 family of sensors and when operating with the constant current sensor excitation the sensor cabling effects are removed from the readings. The RTD/PT100 sensors can be deployed a substantial distance away from the interface card without degrading any measurements. Several hundred meters can be achieved from the sensor to the Interface card without loss in performance of the RTD interfaces. Most different manufacturers sensors for different applications are supported.