CN0287 Datasheet, PDF (7/9 Pages) Analog Devices – Devices Connected

Circuit Note
CN-0287
The gain was set for G = 1, and the excitation current for
380 µA (Pt1000 configuration).
Data was collected, then the jumpers connecting Channel 4,
Channel 3, and Channel 2 were removed sequentially, and data
collected for each condition. The results are shown in Figure 9.
437860
437840
437820
437800
437780
437760
437740
437720
437700
437680
437660
437640
437620
437600
437580
ALL
LEAKAGE
INCLUDED
LEAKAGE
FROM CH4
REMOVED
LEAKAGE
FROM CH3
REMOVED
LEAKAGE
FROM CH2
REMOVED
• The CN-0287 SDP Evaluation Software
• The EVAL-CFTL-6V-PWRZ dc power supply or
equivalent 6 V/1 A bench supply
• A RTD or thermocouple sensor or sensor simulator.
(The evaluation software supports the following
RTDs: Pt100, Pt1000; Thermocouple: Type K, Type J,
Type T, Type S.)
Getting Started
Install the evaluation software by placing the CN-0287
Evaluation Software into the CD drive of the PC. Using My
Computer, locate the drive that contains the evaluation software.
Functional Block Diagram
See Figure 1 for the circuit block diagram and the EVAL-
CN0287-SDPZ-PADSSchematic.pdf file for the complete circuit
schematic. This file is contained in the CN0287 Design Support
Package located at www.analog.com/CN0287-DesignSupport A
functional block diagram of the test setup is shown in Figure 10.
Figure 9. Error Generated by Leakage Current on Channel 1 for 4-Channel
Pt100 RTD with G = 1
The ADC code changed from approximately 437,800 to 437,600
corresponding to a measurement change of 104.9015 Ω to
104.8627, or 0.0388 Ω. This represents a measurement error of
approximately 0.1°C; however it can be removed by calibrating
at room temperature with a fixed input configuration.
COMMON VARIATIONS
The AD779x low noise, low power, 16-/24-bit sigma-delta
ADC family is more suitable for single channel or low power
applications. The ADT7311, ±0.5°C accurate, 16-bit digital SPI
temperature sensor is qualified for automotive applications. The
cold junction compensation circuit accuracy can be improved
by using a digital temperature sensor, such as ADT7320, with
±0.25°C accuracy.
RMS isolation up to 5 kV is be available in the ADuM6401
digital isolator with dc-to-dc converter.
CIRCUIT EVALUATION AND TEST
This circuit uses the EVAL-CN0287-SDPZ circuit board and the
SDP-B (EVAL-SDP-CB1Z) system demonstration platform
controller board. The two boards have 120-pin mating
connectors, allowing for the quick setup and evaluation of the
performance of the circuit. The EVAL-CN0287-SDPZ board
contains the circuit to be evaluated, as described in this note,
and the SDP-B controller board is used with the CN-0287
Evaluation Software to capture the data from the EVAL-
CN0287-SDPZ circuit board.
Equipment Needed
The following equipment is needed:
EVAL-CFTL-6V-PWRZ
6V WALL WART
PC
SENSORS
USB CABLE
CN5 OR J2
CN(x)
JP(x)
120
PINS
USB
OR
SIGNAL
GENERATORS
1.000V
(x) = 1, 2, 3, 4
EVAL-CN0287-SDPZ
BOARD
EVAL-SDP-CB1Z
SDP BOARD
Figure 10. Test Setup Functional Block Diagram
Setup
Connect the 120-pin connector on the EVAL-CN0287-SDPZ
circuit board to the CON A connector on the EVAL-SDP-CB1Z
controller board (SDP-B). Use nylon hardware to firmly secure
the two boards, using the holes provided at the ends of the 120-pin
connectors. With power to the supply off, connect a 6 V power
supply to the +6 V and GND pins on the board. If available, a 6 V
wall wart can be connected to the barrel connector J2 on the
board and used in place of the 6 V power supply. Connect the
USB cable supplied with the SDP-B board to the USB port on
the PC. Do not connect the USB cable to the Mini-USB connector
on the SDP-B board at this time.
Turn on the 6 V power supply to power up the evaluation board
and SDP board, then plug in the Mini-USB cable into the Mini-
USB port on the SDP board.
• A PC with a USB port and Windows® XP (32 bit),
Windows Vista®, or Windows® 7
• The EVAL-CN0287-SDPZ circuit board
• The EVAL-SDP-CB1Z SDP-B controller board
Rev. C | Page 7 of 9