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单片机温度计英文文献和翻译

时间:2016-12-28 12:46来源:毕业论文
单片机基于Anderson回路和Pt-100传感器的小型高精度数字温度计英文文献和翻译

AbstractA  simple and practical digital thermometer with  an
accuracy better than 0.1 T  over a near-rooin-temperature
(from  -10 "C  to  50 "C)  measurement range has been
developed.  The instrument is compact and battery
operated and provides for both digital and analog outputs.
A four-lead platinum thermal sensor, driven by a constant
current  loop,  allows  for  accurate temperature readings
with high immunity to the contact resistances and to their
variations. A low-noise electronics allows for temperature
measurements with a 1-nK  resolution. By experimentally
characterizing the non-linearity of  the  adopted Pt-100
sensor, a suitable readout correction table  has  been
calculated in order  tal  compensate  for  the sensor
non-linearity. This compensating procedure allows for  a
wider (from  -50 "C  to  +200 "C)  and  higher accuracy
(-0.05  "C) measurement range. The accuracy, up to now,
IS  essentially limited by the  accuracy of  the  temperature
standard  used for calibration.4827
1. Initroduction
Temperature measurements characterized by  the best
accuracy  levels use platinum sensors  to  transduce the
thermal  signal into an electric one  [l].  The low  thermal
coefficient  (a  = l/R-dR/dT  z  0.385 Yd"C  for  standard
commercial  probes  121)  and  the relatively  low  ohmic
value  of  these sensors push toward the  need  for  high-
resolution measurements of  the variation in the sensor
resistance.  Such  measurements require a careful
consideration of  the additional resistances  arising  from
the lead wires  and  contact  weldings  arid  from the
associated thermal  mi;.  For  this  reason, the  most
accurate resistance measurements need four-wires
probes [3].  With  a  four-wire resistor the voltage
difference between the high-impedance voltmetric
terminals can be read, essentially without spurious
resistance effects, when a constant current is flowing
trough the other  mperometric wires and terminals.  A
particular and quite recent application of  this concept is
exploited in the Anderson's loop circuit [4]. This current- 4-lead thermistor  Analog ovtput
Km
Measurement
electronic  circuR
Figure 1. Block diagram of the digital thermometer.
sensor, the main electronic sections, and both outputs,  is
depicted  in Fig. 1, while  the details of  the measurement
electronic circuit are indicated in Fig. 2. The excitation
current is  obtained by  means  of  a precise 5-V voltage
reference (Linear Technology,  LT1236), an  ultra  low
noise  operational amplifier (Analog Device, OP177), and
a  reference  resistor  R2=100S.1 R  (3 ppm/"C).  The
doubly  differential subtraction section is  made  of  two
instrumentation amplifiers (Burr Brown, INAl18) and of
another OP177  operational amplifier. As  a temperature
sensor,  a four-wire  Pt-100 commercial  and cheap
thermistor (RS, 237-1657) has been used. This sensor, in
compliance with  BS1904:1984 class  B  quality,  is
characterized  by  a  nominal-resistance  value  of
Ro  = 10033.1  R  at  a  reference  temperature T,=O  "C  and 单片机温度计英文文献和翻译:http://www.youerw.com/fanyi/lunwen_1615.html
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