Microchip Technology PT100 RTD, Руководство пользователя

Страница: 11 / 26

PT100 RTD EVALUATION
BOARD USER’S GUIDE
©
2006 Microchip Technology Inc. DS51607A-page 7
Chapter 2. Installation and Operation
2.1 INTRODUCTION
The PT100 RTD Evaluation Board allows the user to evaluate Microchip’s solution to
accurately measure temperature using RTD. When biasing RTDs to measure
temperature, self-heat due to power dissipation has to be considered. RTD resistance
availability typically ranges from 100
Ω
to 5,000
Ω
. In order to measure the output
voltage across the RTD over a wide temperature range, the biasing current has to be
relatively high. This higher current causes more power dissipation through heat and
skews the temperature reading. Microchp’s solution to this challenge is to use an
MCP6S26 Programmable Gain Amplifier (PGA) to increase the sensor dynamic output
range and increase measurement resolution while significantly reducing the biasing
current magnitude.
This board consists of a surface mount RTD to measure the PCB temperature. In
addition, the user can connect and measure an external leaded RTD (2, 3 or 4-Wire)
and configure the corresponding jumper to remotely measure temperature. The
multiple input channel PGA adds gain programmability into the analog circuit. The
multiple input channels are used to switch between RTDs and the gain is used to
increase the sensor dynamic range.
The PGA output is connected to a differential amplifier circuit which allows the user to
scale the sensor output. The differential output is digitized using an MCP3301 12-bit
differential analog-to-digital converter. The data is transmitted to the PC using the USB
interface. A Microsoft Excel-based Graphical User Interface (GUI) is used to obtain and
display the data in real-time.
2.2 FEATURES
The PT100 RTD Evaluation Board has the following features:
• A surface mount PT100 RTD
• External (2, 3 or 4-wire) RTD connector
• Gain and input channel programmability using MCP6S26 PGA
• MCP3301 12-Bit + sign ADC
• MCP41010 10 k
Ω
Digital Potentiometer
• PIC18F2550 PICmicro
®
Microcontroller
• USB interface to PC
• Microsoft Excel-Based GUI