Pico Pt-104 User manual

PT-104

User Guide

PT104-2

Temperature Converter

Contents

.............................................................................................3

1 Introduction

...................................................................................................3

1 Overview

...................................................................................................4

2 Safety warning

...................................................................................................5

3 Legal information

.............................................................................................6

2 Product information

...................................................................................................6

1 Specifications

...................................................................................................6

2 Installing the driver

...................................................................................................7

3 Connection

...................................................................................................10

4 Background on PRTs

.............................................................................................12

3 Driver information

...................................................................................................12

1 Introduction

...................................................................................................13

2 pt104_open_unit

...................................................................................................13

3 pt104_close_unit

...................................................................................................13

4 pt104_poll_driver

...................................................................................................14

5 pt104_get_cycle

...................................................................................................15

6 pt104_set_channel

...................................................................................................15

7 pt104_set_mains

...................................................................................................16

8 pt104_get_value

...................................................................................................17

9 pt104_get_version

...................................................................................................17

10 pt104_get_unit_info

...................................................................................................17

11 pt104_get_driver_version

...................................................................................................18

12 pt104_labview

...................................................................................................18

13 Windows 95/98/ME/NT/2000/XP

...................................................................................................18

14 Linux

.............................................................................................19

4 Writing your own programs

...................................................................................................19

1 C / C++

...................................................................................................20

2 Delphi

...................................................................................................20

3 Excel

...................................................................................................20

4 LabVIEW

...................................................................................................21

5 Visual Basic

...................................................................................................21

6 Agilent-VEE

.............................................................................................22

5 Technical reference

...................................................................................................22

1 Serial port settings

...................................................................................................22

2 Serial port connections

...................................................................................................23

3 Protocol information

...................................................................................................25

4 Modem operation

...................................................................................................26

5 Lookup table

PT-104 Help

PT104-2

......................................................................................................31

Index

Contents

PT104-2

PT-104 Help

1Introduction

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.

Introduction 4

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 Limited or their

authorised distributors.

PT-104 Help

1.3 Legal information

The material contained in this release is licensed, not sold. Pico Technology Limited

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.

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 Limited, 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.

Product information 6

2Product information

2.1 Specifications

Temperature

Resistance

Voltage

Sensor

PT100*, PT1000

N/A

Range

-200 to 800°C

0 to 375

0 to 10k

0 to 115

mV;

0 to 2.5

Linearity

10 ppm

Accuracy @25°C

0.01°C*

20 ppm*

0.2%*

Temperature

coefficient

3 ppm/°C

100

ppm/°C

RMS Noise

(using filter)

0.01°C

10 ppm

Resolution

0.001°C

0.156

Conversion Time Per

Channel

720 ms**

180 ms

Number of inputs

Connectors

4-pin mini-DIN

Input impedance

>>1M

Overvoltage

protection

±30 V

Output

RS232, DE9 female

Environmental

20 to 30°C for stated accuracy; 0 to 70°C overall; 20 to 90%

Software

PicoLog data logging software; Drivers for Windows

95/98/NT/2000/ME; 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

PT-104 Help

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

PT100, PT1000

4 Wire

PT100, PT1000

3 Wire

PT100, PT1000

2 Wire

Differential voltage

White

Connect to pin 3

Do not connect

Red

V -

White

V +

Red

Connect to pin 2

Gnd

Single-ended voltage connection

Connector

Channel

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 MiniDIN socket consists of a 100

resistor to mains

earth/ground via the serial cable outer braiding and the PC chassis.

Product information 8

Setting up

To set up the unit, do the following:

From the PicoLog Recorder

File

menu, select

New settings.

The

Recording

dialog box appears:

Click

The

Sampling Rate

dialog box appears:

Click

The

Converter details

dialog box appears:

From the

Converter type

drop-down list, select

PT-104

PT-104 Help

From the

Port

drop-down list, select the port and click

After a short while, the

PT-104 channels

window appears:

In the

PT-104 channels

window, double-click on

Ch1 unused

The

Edit PT-104 Channel

dialog box appears:

Type in a name for the channel, if required

Select the data type required i.e temperature, resistance or voltage

Select circuit - for PT100 and PT1000

10.

Now click

Readings from the PT-104 should appear in the monitor window:

Product information 10

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

at 0°C and 138.4

at 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

change 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

A through a 100

resistor 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

per core.

PT-104 Help

The type of probe and cable should be chosen carefully to suit the application. The

main issues are the temperature range and exposure to fluids (corrosive or

conductive) or metals. Clearly, normal solder junctions on cables should not be used at

temperatures above about 170°C.

Sensor manufacturers offer a wide range of sensors that comply with BS1904 class B

(DIN 43760). These sensors offer an accuracy of ±0.3°C at 0°C. For increased

accuracy, you can use BS1904 class A (±0.15°C) or tenth-DIN sensors (±0.03°C).

Companies like Isotech can provide standards with 0.001°C accuracy. Please note that

these accuracy specifications relate to the SENSOR ONLY: it is necessary to add on any

error in the measuring system as well.

Related standards are IEC751 and JISC1604-1989. IEC751 also defines the colour

coding for PRT sensor cables: the one or two wires atttached to one end of the sensor

are red, and the one or two wires at the other end are white.

Driver information 12

3Driver information

3.1 Introduction

The PT-104 is supplied with driver routines that you can build into your own programs.

Once you have installed the software, the

Drivers

directory contains the drivers and

a selection of examples of how to use the drivers. It also contains a copy of this

manual as a PDF file.

The driver routine is supplied as a Windows DLL.

The Windows DLL can be used with C, C++, Delphi and Visual Basic programs: it can

also be used with programs like Microsoft Excel, where the macro language is a form

of Visual Basic. More than one application can access the Windows DLL at the same

time, as long as the applications do not change the settings for channels that they are

not using.

These are the routines in the driver:

pt104_open_unit

Open the device on a specified serial port.

pt104_close_unit

Close the port (do this each time you finish using the

device!)

pt104_poll_driver

Poll the driver (not usually necessary).

pt104_get_cycle

Find out when the driver has taken a new set of

readings.

pt104_set_channel

Specify the sensor type and filtering for a channel.

pt104_set_mains

Specify the mains setting 50 or 60 Hz. This enables the

product to reject mains-frequency interference signals.

pt104_get_value

Get the most recent data reading from a channel.

pt104_get_version

Get the version number of this PT-104.

pt104_get_unit_info

Get the version number, batch number and calibration

number and date of this PT-104.

pt104_get_driver_version

Get the version number of the driver.

pt104_labview

Easy to use interface for LabVIEW.

The normal calling sequence for these routines is as follows:

1. Open driver

2. Set Channels

3. While you want to read data

4. Get data

5. End While

6. Close Unit

7. Close Driver

PT-104 Help

3.2 pt104_open_unit

short pt104_open_unit ( short port );

This routine specifies the serial port number with a PT-104 unit. If you wish to use

more than one PT-104, you should call the routine once for each PT-104.

Arguments:

port

- t

he port must be 1 for COM1, 2 for COM2, and so on

Returns:

TRUE

- if the driver

successfully opens the PT-104

3.3 pt104_close_unit

void pt104_close_unit (unsigned short port);

This routine disconnects the driver from the specified serial port.

If you successfully open any serial ports, you MUST call

pt104_close_unit

for each

port before you exit from your program. If you do not, your computer may misbehave

until you next reboot it.

Arguments:

port

- the port number. T

he port must be 1 for COM1, 2 for COM2, and so on

Returns:

none

3.4 pt104_poll_driver

void pt104_poll_driver (void);

It is not normally necessary to call this routine, as the driver uses the timer to poll the

PT-104. Some programs, like Excel, appear to block the timer, so it is necessary to poll

the driver periodically whilst waiting for data.

Arguments:

none

Returns:

none

Driver information 14

3.5 pt104_get_cycle

unsigned short pt104_get_cycle(

unsigned long far

*cycle,

unsigned short

port);

This routine returns the number of complete cycles of readings taken from a particular

PT-104

When you call

pt104_get_value

, it returns immediately with the most recent reading

for the specified channel. If you call it repeatedly, it will return the same reading

repeatedly, until the driver takes the next reading from that channel.

If you wish to record values only when the driver has taken a new reading, you can

use this routine to find out how many complete cycles of readings the driver has

taken, then you can call

pt104_get_value

only when a cycle has completed.

Note: Each PT-104 is polled independently, so the cycle numbers for multiple PT-104s

may not keep in step.

Arguments:

cycle

- a pointer to an array where the cycle numbers are stored

port

- the port number. T

he port must be 1 for COM1, 2 for COM2, and so on

Returns:

- a value representing the number of complete cycles of readings taken

from a particular PT-104

PT-104 Help

3.6 pt104_set_channel

short pt104_set_channel (

unsigned short port,

unsigned short channel,

unsigned short data_type

unsigned short no_of_wires);

You should call this routine once for each channel that you would like to take readings

from. You can do this any time after calling

pt104_open_unit.

The fewer channels are selected, the more frequently these channels will be updated.

It takes about 1 second per active channel.

If a call to pt104_set_channel has a data_type of single ended, then the channel

specified's 'sister' channel is also enabled eg, enabling 3 will also enable 7.

Arguments:

channel

- specifies which channel you want to set the details for: it should be

between 1 and 4 if using single ended inputs in voltage mode

data_type

- set to the type of reading you require (1 for PT100, 2 for PT1000, 3

for resistance 0 to 500R, 4 for resistance 0 to 10k, 5 for differential

voltage 0 to 100 mV, 6 for differential voltage 0 to 2.5 V, 7 for single

ended voltage 0 to 100 mv and 8 for single ended voltage 0 to 2.5 V

no_of_wires

- specifies how many wires the PT100 or PT1000 has (set to 2, 3 or

Returns:

TRUE

- if the channel was successfully set

3.7 pt104_set_mains

void pt104_set_mains (unsigned short sixty_hertz);

This routine is used to select the mains frequency of 50 or 60 Hz.

Choosing the incorrect frequency may increase susceptibility to electrical noise.

Arguments:

sixty_hertz

- for 50 Hz set this to 0

- for 60 Hz set this to 1

Returns:

none

Driver information 16

3.8 pt104_get_value

short pt104_get_value (

long far

*data,

unsigned short

port,

unsigned short

channel,

unsigned short

filtered);

Once you open the driver and define some channels, the driver begins to take

continuous readings from the PT-104. When you call this routine, it immediately sets

data to the most recent reading for the specified channel.

Temperatures are returned in thousandths of a degree Celsius, voltages in the 2.5 V

range are returned in tens of nanovolts (2.5 V returned as 250 000 000 * 10 nV),

voltages in the 115 mV range are returned in nanovolts and resistances in milliohms.

When measuring single-ended voltages:

connector 1 pin 2 is channel 1

connector 2 pin 2 is channel 2

...

connector 1 pin 3 is channel 5

connector 2 pin 3 is channel 6

Arguments:

data

- a pointer to an array where the sample values will be stored

port

- the port number. T

he port must be 1 for COM1, 2 for COM2, and so on

channel

- returns a reading from Channel 1

- returns a reading from Channel 2

- returns a reading from Channel 3

- returns a reading from Channel 4

filtered

- i

f set to TRUE, the driver returns a low-pass filtered value of the

temperature. The time constant of the filter depends on the value of

filter_factor for this channel, and on how many channels are active

Returns:

TRUE

FALSE

- if a reading is available

- if any of the inputs are out of range. It will normally return

FALSE

for

a few seconds after you open the driver, until the driver has taken a

reading from the specified channel

PT-104 Help

3.9 pt104_get_version

unsigned short pt104_get_version (

unsigned short far

*version,

unsigned short

port);

This routine sets version to version number of the specified PT-104.

Arguments:

version

- driver version.

The upper byte of the version is always 104 for a PT-

104; the lower byte is the two hex digits of the version and release. It

provides a useful check that the link to the PT-104 is working correctly

port

- the port number. T

he port must be 1 for COM1, 2 for COM2, and so on

Returns:

TRUE

- if the parameters are in range

3.10 pt104_get_unit_info

short pt104_get_unit_info (

char

*str,

unsigned short

line,

unsigned short

port)

Call this routine to obtain information on the unit.

str

is set to the infomation

specified by

line

Arguments:

str

- a pointer to a char array that is to receive the information

line

- 0 for version number, 1 for calibration number, 2 for calibration date,

3 for batch number

port

- the port number. T

he port must be 1 for COM1, 2 for COM2, and so on

Returns:

- the number of bytes written to

str

3.11 pt104_get_driver_version

short pt104_get_driver_version (void)

Arguments:

none

Returns:

the version number of the current driver

Driver information 18

3.12 pt104_labview

short pt104_labview (

float

*result,

unsigned short

port,

unsigned short

channel,

unsigned short

data_type,

unsigned short

filtered

unsigned short

no_of_wires)

This is an easy-to-use interface for LabVIEW. To gain a thorough understanding of the

capabilities of this routine, see the example program supplied with the software.

Arguments:

result

- a pointer to a float that is to receive the result

port

- the port number. T

he port must be 1 for COM1, 2 for COM2, and

so on

channel

- 1 for Channel 1, 2 for Channel 2, 3 for Channel 3, and so on

data_type

set to the type of reading you require (1 for PT100, 2 for PT1000,

3 for resistance 0 to 500R, 4 for resistance 0 to 10k, 5 for

differential voltage 0 to 100 mV, 6 for differential voltage 0 to 2.5

V, 7 for single ended voltage 0 to 100 mV and 8 for single ended

voltage 0 to 2.5 V

filtered

- i

f set to TRUE, the driver returns a low-pass filtered value of the

temperature. The time constant of the filter depends on the value

filter_factor

for this channel, and on how many channels are

active

no_of_wires

- specifies how many wires the PT100 or PT1000 has (set to 2, 3 or

Returns:

- if successful;

- if unsuccessful

3.13 Windows 95/98/ME/NT/2000/XP

The 32-bit Windows driver is the file

pt10432.DLL

: it is installed in the

drivers\win32

directory. If an application is unable to find the DLL, try moving the DLL to

windows\system

3.14 Linux

At time of release, Linux is not supported. Please check

http://www.picotech.com/drivers.html

for updates.

PT-104 Help

4Writing your own programs

4.1 C / C++

You should find the following files in the directory where your software is installed.

pt104tes.c

- Demonstration file.

pt10432.dll

- Windows 32-bit driver.

pt104.h

- header file

Producing a library file (

.lib

)

For Borland and Watcom C, Microsoft Visual C version 1.5 or lower, use the implib

program that comes supplied with these compilers.

The command is:

Implib pt10432.lib pt10432.dll

This command is typed in at the command prompt - make sure you are in the correct

directory or the

pt10432.dll

file will not be found. This will create a file called

pt10432.lib

The following steps are then required to use the drivers in your program:

Include the

pt10432.lib

in your program

Include the file

pt104.h

in the source file(s) of your program.

The

pt104tes.c

file can be used to demonstrate using the PT-104 driver program

within a Windows application. You will also need to include the resource file

pt104tes.rc.

For Microsoft Visual C versions 2, 4 and 5, Microsoft no longer supply

implib

Furthermore, the names used in these versions of C are decorated - there is a prefix

which indicates how many bytes are transferred to the routine as parameters. As a

result, the C names do not match the names in the DLL. The Microsoft tools to alias

decorated to undecorated names do not appear to work, so it is therefore necessary to

use ordinal linking- linking by number, rather than name. The file

pt104ms.lib

(supplied with examples) contains all the neccessary routines. To use this file:

Include the

pt104ms.lib

in your project

Include the file

pt104.h

in the C source file(s) of your program.

C++

C++ programs can access all versions of the driver. If

pt104.h

is included in a C++

program, the

PREF1

macro expands to

extern "C"

: this disables name-decoration

and enables C++ routines to make calls to the driver routines using C headers.

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