PICO PT-104 User manual

Copyright 2005-9 Pico Technology Ltd. All rights reserved.
PT-104
User's Guide
pt104.en-5
Thermistor Converter

PT-104 User's GuideI
Copyright 2005-9 Pico Technology Ltd. All rights reserved.pt104.en
Contents
.....................................................................................................................................11 Introduction
...........................................................................................................................................1
1 Overview
...........................................................................................................................................2
2 Safety warning
...........................................................................................................................................3
3 Legal information
.....................................................................................................................................42 Product information
...........................................................................................................................................4
1 Specifications
...........................................................................................................................................4
2 Installing the driver
...........................................................................................................................................5
3 Connection
...........................................................................................................................................8
4 Background on PRTs
.....................................................................................................................................103 Driver information
...........................................................................................................................................10
1 Introduction
...........................................................................................................................................11
2 pt104_open_unit
...........................................................................................................................................11
3 pt104_close_unit
...........................................................................................................................................11
4 pt104_poll_driver
...........................................................................................................................................12
5 pt104_get_cycle
...........................................................................................................................................12
6 pt104_set_channel
...........................................................................................................................................13
7 pt104_set_mains
...........................................................................................................................................13
8 pt104_get_value
...........................................................................................................................................14
9 pt104_get_version
...........................................................................................................................................14
10 pt104_get_unit_info
...........................................................................................................................................14
11 pt104_get_driver_version
...........................................................................................................................................15
12 pt104_labview
...........................................................................................................................................15
13 Windows XP (SP2)/Vista
...........................................................................................................................................15
14 Linux
.....................................................................................................................................164 Writing your own programs
...........................................................................................................................................16
1 C / C++
...........................................................................................................................................17
2 Delphi
...........................................................................................................................................17
3 Excel
...........................................................................................................................................17
4 LabVIEW
...........................................................................................................................................18
5 Visual Basic
...........................................................................................................................................18
6 Agilent VEE
.....................................................................................................................................195 Technical reference
...........................................................................................................................................19
1 Serial port settings
...........................................................................................................................................19
2 Serial port connections
...........................................................................................................................................20
3 Protocol information
...........................................................................................................................................22
4 Modem operation
...........................................................................................................................................22
5 Lookup table
..............................................................................................................................................28
Index

Introduction 1
Copyright 2005-9 Pico Technology Ltd. All rights reserved. pt104.en
1 Introduction
1.1 Overview
The PT-104 is a four-channel, high-resolution
temperature converter for use with PT100 and PT1000
type sensors. It can be used to measure temperature,
resistance and voltage.
In PT100/PT1000/resistance mode, the unit uses a four-
wire circuit.
In voltage mode, the input connector can be treated as
a differential input with ground, or two single-ended
inputs. Both inputs must be 0 V or above, though it
does not matter which input has the higher voltage. For
the 115 mV range, the accuracy may vary by 2%, and
the temperature coefficient will be 100 ppm/°C.

PT-104 User's Guide2
Copyright 2005-9 Pico Technology Ltd. All rights reserved.pt104.en
1.2 Safety warning
We strongly recommend that you read the general safety information below before
using your product for the first time. If the equipment is not used in the manner
specified, then the protection provided may be impaired. This could result in damage
to your computer and/or injury to yourself or others.
Maximum input range
The PT-104 is designed to measure voltages in the range 0 to +2.5 V. Any voltages in
excess of ±30 V may cause permanent damage to the unit.
Mains voltages
Pico products are not designed for use with mains voltages. To measure mains we
recommend the use of a differential isolating probe specifically designed for such
measurements.
Safety grounding
The ground of every product is connected directly to the ground of your computer via
the interconnecting cable provided. This is done in order to minimise interference. If
the PC (especially laptop) is not grounded, reading stability cannot be guaranteed and
it may be necessary to manually ground the equipment.
As with most oscilloscopes and data loggers, you should take care to avoid connecting
the inputs of the product to anything which may be at a hazardous voltage. If in
doubt, use a meter to check that there is no hazardous AC or DC voltage. Failure to
check may cause damage to the product and/or computer and could cause injury to
yourself or others.
Take great care when measuring temperatures near mains equipment. If a sensor is
accidentally connected to mains voltages, you risk damage to the converter or your
computer and your computer chassis may become live.
You should assume that the product does not have a protective safety earth. Incorrect
configuration or use of the device to measure voltages outside the maximum input
range can be hazardous.
Repairs
The unit contains no user-serviceable parts. Repair or calibration of the unit requires
specialised test equipment and must be performed by Pico Technology or its
authorised distributors.

Introduction 3
Copyright 2005-9 Pico Technology Ltd. All rights reserved. pt104.en
1.3 Legal information
The material contained in this release is licensed, not sold. Pico Technology grants a
licence to the person who installs this software, subject to the conditions listed below.
Access
The licensee agrees to allow access to this software only to persons who have been
informed of these conditions and agree to abide by them.
Usage
The software in this release is for use only with Pico products or with data collected
using Pico products.
Copyright
Pico Technology Limited claims the copyright of, and retains the rights to, all material
(software, documents etc.) contained in this release. You may copy and distribute the
entire release in its original state, but must not copy individual items within the
release other than for backup purposes.
Liability
Pico Technology and its agents shall not be liable for any loss, damage or injury,
howsoever caused, related to the use of Pico Technology equipment or software,
unless excluded by statute.
Fitness for purpose
No two applications are the same: Pico Technology cannot guarantee that its
equipment or software is suitable for a given application. It is your responsibility,
therefore, to ensure that the product is suitable for your application.
Mission-critical applications
This software is intended for use on a computer that may be running other software
products. For this reason, one of the conditions of the license is that it excludes usage
in mission-critical applications, for example life support systems.
Viruses
This software was continuously monitored for viruses during production. However,
you are responsible for virus-checking the software once it is installed.
Support
If you are dissatisfied with the performance of this software, please contact our
technical support staff, who will try to fix the problem within a reasonable time scale.
If you are still dissatisfied, please return the product and software to your supplier
within 14 days of purchase for a full refund.
Upgrades
We provide upgrades, free of charge, from our web site at www.picotech.com. We
reserve the right to charge for updates or replacements sent out on physical media.
Trademarks
Pico Technology Limited, PicoScope, PicoLog, DrDAQ and EnviroMon are trademarks of
Pico Technology, registered in the United Kingdom and other countries.
Pico Technology acknowledges the following product names as trademarks of their
respective owners: Windows, Excel, Visual Basic, LabVIEW, Agilent VEE, Delphi.

PT-104 User's Guide4
Copyright 2005-9 Pico Technology Ltd. All rights reserved.pt104.en
2 Product information
2.1 Specifications
Temperature
Resistance
Voltage
Sensor
PT100*, PT1000
N/A
N/A
Range
-200 to 800°C
0 to 375 W*;
0 to 10 kW
0 to 115 mV;
0 to 2.5 V*
Linearity
10 ppm
10 ppm
10 ppm
Accuracy @25°C
0.01°C*
20 ppm*
0.2%*
Temperature
coefficient
3 ppm/°C
3 ppm/°C
100 ppm/°C
RMS Noise
(using filter)
0.01°C
10 ppm
10 ppm
Resolution
0.001°C
1 mW
0.156 mV
Conversion Time
Per Channel
720 ms**
720 ms**
180 ms
Number of inputs
4
Connectors
4-pin mini-DIN
Input impedance
>> 1 MW
Overvoltage
protection
±30 V
Output
RS-232, DE9 female
Environmental
20 to 30°C for stated accuracy; 0 to 70°C overall; 20 to 90% RH
Dimensions
W 135 mm x L 184 mm x H 36 mm
(5.31" x 7.24" x 1.42")
Software
PicoLog data logging software; Drivers for Windows XP SP2/
Vista; Examples for C/C++, Delphi, Excel, LabVIEW, Visual Basic,
Agilent-VEE.
Quoted accuracy is for options marked *
For four-wire temperature and resistance measurement**
2.2 Installing the driver
The driver is installed automatically when you install the PicoLog software.
Alternatively, you can download the driver from our website at http://www.picotech.
com.

Product information 5
Copyright 2005-9 Pico Technology Ltd. All rights reserved. pt104.en
2.3 Connection
To use the PT-104, you should connect its D-connector to your computer's serial port
using the cable provided. Next, connect a PT100 or PT1000 PRT to one of the input
connectors.
Pin Connections to the PT-104 Mini-DIN socket
Pin
PT100, PT1000
4 Wire
PT100, PT1000
3 Wire
PT100, PT1000
2 Wire
Differential voltage
1
White
Connect to pin 3
Connect to pin 3
Do not connect
2
Red
Red
Red
V -
3
White
White
White
V +
4
Red
Red
Connect to pin 2
Gnd
Single-ended voltage connection
Single-ended mode allows you to double the number of channels from 4 to 8. It is
supported by the driver, so you can use it in your own applications. It is not,
however, supported by PicoLog.
Connector
Channel
Pin
1
1
3
5
2
2
2
3
6
2
3
3
3
7
2
4
4
3
8
2
Note on Differential Voltage Mode
The maximum input voltage range of the PT-104 is 2.5 V. Any voltage in excess
of +/-30 V on any input pin may cause permanent damage to the unit.
In Differential Voltage Mode, the input connector should be treated as a differential
input with reference to ground. Both inputs (V+ and V-) must be zero volts or above
(it does not matter which input has the higher voltage) and must remain within the
input range. A ground reference connection is also required for correct operation. The
ground connection of each mini-DIN socket consists of a 100 Wresistor to mains
earth/ground via the serial cable outer braiding and the PC chassis.

PT-104 User's Guide6
Copyright 2005-9 Pico Technology Ltd. All rights reserved.pt104.en
Setting up
To set up the unit, do the following:
1. From the PicoLog Recorder File menu, select New settings. The Recording
dialog box appears:
2. Click OK. The Sampling Rate dialog box appears:
3. Click OK. The Converter details dialog box appears:
4. From the Converter type drop-down list, select PT-104.

Product information 7
Copyright 2005-9 Pico Technology Ltd. All rights reserved. pt104.en
5. From the Port drop-down list, select the port and click OK. After a short while,
the PT-104 channels window appears:
6. In the PT-104 channels window, double-click on Ch1 unused. The Edit PT-
104 Channel dialog box appears:
7. Type in a name for the channel, if required
8. Select the data type required i.e temperature, resistance or voltage
9. Select circuit - for PT100 and PT1000
10. Now click OK. Readings from the PT-104 should appear in the monitor window:

PT-104 User's Guide8
Copyright 2005-9 Pico Technology Ltd. All rights reserved.pt104.en
2.4 Background on PRTs
PRTs (Platinum Resistance Thermometers) offer excellent accuracy over a wide
temperature range (from -200 to 850°C). Sensors are interchangeable between
different manufacturers, and are available in various accuracy ratings in packages to
suit most applications. Unlike thermocouples, it is not necessary to use special cables
to connect to the sensor.
The principle of operation is to measure the resistance of a platinum element. The
most common type (PT100) has a resistance of 100 Wat 0°C and 138.4 Wat 100°C.
The relationship between temperature and resistance is approximately linear over a
small temperature range: for example, if you assume that it is linear over the 0 to
100°C range, the error at 50°C is 0.4°C. For precision measurement, it is necessary
to linearise the resistance to give an accurate temperature. The most recent definition
of the relationship between resistance and temperature is International Temperature
Standard 90 (ITS-90). This linearisation is done automatically with software.
The linearisation equation is:
Rt = R0 * (1 + A* t + B*t2 +C*(t-100)* t3)
A = 3.9083 E-3
B = -5.775 E-7
C = (below 0°C) -4.183 E -12
(Above 0°C) zero
For a PT100 sensor, a 1°C temperature change will cause a 0.384 Wchange in
resistance, so even a small error in measurement of the resistance (for example, the
resistance of the wires leading to the sensor) can cause a large error in the
measurement of the temperature. For precision work, sensors have four wires - two
to carry the sense current, and two to measure the voltage across the sensor
element. It is also possible to obtain three-wire sensors, although these operate on
the (not necessarily valid) assumption that the resistance of each of the three wires is
the same.
The current through the sensor will cause some heating. For example, a sense
current of 245 µA through a 100 Wresistor will generate 6 µW of heat. If the sensor
element is unable to dissipate this heat, it will report an artificially high temperature.
This effect can be reduced by either using a large sensor element, or by making sure
that it is in good thermal contact with its environment.
Using a 1 mA sense current will give a signal of only 100 mV. Because the change in
resistance for a degree Celsius is very small, even a small error in the measurement
of the voltage across the sensor will produce a large error in the temperature
measurement. For example, a 100 µV voltage measurement error will give a 0.4°C
error in the temperature reading. Similarly, a 1 µA error in the sense current will give
0.4°C temperature error.
Because of the low signal levels, it is important to keep any cables away from electric
cables, motors, switchgear and other devices that may emit electrical noise. Using
screened cable, with the screen grounded at one end, may help to reduce
interference. When using long cables, it is necessary to check that the measuring
equipment is capable of handling the resistance of the cables. Most equipment can
cope with up to 100 Wper core.