Measurement CIO-DAS-TEMP User Manual

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CIO-DAS-TEMP

Temperature Input Board

User’s Guide

Revision 4, November, 2000

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HM CIO-DAS-TEMP.doc

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Table of Contents

1 INTRODUCTION ................................................................

2 INSTALLATION .................................................................

3 INTERFACING ..................................................................

4 PROGRAMMING AND APPLICATIONS ...........................................

5 THEORY OF OPERATION .......................................................

6 REGISTER MAP .................................................................

7 SPECIFICATIONS ..............................................................

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12.1 SOFTWARE ................................................................

12.2 HARDWARE ................................................................

33.1 CONNECTOR DIAGRAM .....................................................

33.2 CONNECTING THE AD592 SENSORS ..........................................

44.1 PROGRAMMING LANGUAGES ...............................................

44.2 PACKAGED APPLICATION PROGRAMS .......................................

55.1 OVERVIEW .................................................................

65.2 SIGNAL RESOLUTION AND CONVERSION SPEED ..............................

75.3 OPERATION OF THE COUNTERS ..............................................

75.4 LINE NOISE REJECTION .....................................................

96.1 CONTROL REGISTERS .......................................................

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1 INTRODUCTION

The CIO-DAS-TEMP is a temperature measurement board desig ned for use with the A D592 semiconductor temperature sensor. Since the AD592 is a current output dev ice, the on-board signal conditioning is optimized for that sensor. A voltage-to-frequency converter translates the signal from the sensor into a v alue proportional to tem perature. Functions in the Univ ersal Library convert that proportional value into a temperature reading on which you can base a control system, or simply log for later analysis.

The AD592 semiconductor temperature sensor is ideally suited for measurements in the ambient range. If you are designing an HVAC system, or need to monitor the efficiency of an existing system, the CIO-DAS-TEMP provides the best value and accuracy in the ambient range. More accurate than thermocouples and less expensive than RTDs, the AD592 sensor is available through general distribution or from Measurement Computing Corp. as an individual part or in a stainless steel probe.

Custom Ranges

The CIO-DAS-TEMP is a current input board with a fixed range of 0 to 500 µAmps. The front end may be customized to allow up to 0 to 20 mA. T he CIO-DAS-TEMP provides up to a full 16 bits of resolution and will easily reject line noise. If you have a current m easurement application and want a precisely matched front end, please call our technical support and explain your needs to us.

2 INSTALLATION

2.1 SOFTWARE

There is a bank of switches to set before installing the board in your computer. By far the simplest way to configure your board is to use the InstaCal

InstaCal

will show you all available options, how to configure the switches to match your application requirements, and will create a configuration file that your application software (and the Universal Library) will refer to so the software you use w ill automatically know the exact configuration of the board.

Please refer to the Software Installation Manual regarding the installation and operation of InstaCal The following hard copy information is provided as a matter of completeness, and will allow you to set the hardware configuration of the board if y ou do not have immediate access to InstaCal computer.

program provided as part of y our software pack age.

and/or your

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2.2 HARDWARE

2.2.1 Base I/O Address

The CIO-DAS-TEMP may be set to operate at any one of a range of base addresses. T he CIO-DAS-TEMP uses eig ht, 8-bit addresses, so the base addresses available are in steps of eig ht. For example, 300h, 308h, 310h and so on. Table 2-1 of occupied PC addresses below should be supplemented by information you provide about the addresses used by any other boards or devices installed in your computer. After all occupied addresses are known, choose an available block of eight I/O addresses for your CIO-DAS-TEMP. Make sure it is on a 3-bit (8-address) boundary.

Table 2-1. PC I/O Addresses

FUNCTION HEX RANGEFUNCTIONHEX RANGE

EGA 2C0-2CF8237 DMA #1000-00F EGA2D0-2DF8259 PIC #1020-021 GPIB (AT) 2E0-2E78253 TIMER040-043 SERIAL PORT 2E8-2EF82C55 PPI (XT)060-063 SERIAL PORT 2F8-2FF8742 CONTROLLER (AT)060-064 PROTOTYPE CARD 300-30FCMOS RAM & NMI MASK (AT)070-071 PROTOTYPE CARD310-31FDMA PAGE REGISTERS080-08F HARD DISK (XT) 320-32F8259 PIC #2 (AT)0A0-0A1 PARALLEL PRINTER378-37FNMI MASK (XT)0A0-0AF SDLC 380-38F8237 #2 (AT)0C0-0DF SDLC 3A0-3AF80287 NUMERIC CO-P (AT)0F0-0FF MDA 3B0-3BBHARD DISK (AT)1F0-1FF PARALLEL PRINTER3BC-3BFGAME CONTROL200-20F EGA 3C0-3CFEXPANSION UNIT (XT)210-21F CGA 3D0-3DFBUS MOUSE238-23B SERIAL PORT 3E8-3EFALT BUS MOUSE23C-23F FLOPPY DISK 3F0-3F7PARALLEL PRINTER270-27F SERIAL PORT3F8-3FFEGA2B0-2BF

The Base Address is set by a switch on the CIO-DAS-TEMP labeled ADDRESS. The CIO-DAS-TEMP uses eight, 8 bit addresses.

The board is set at the factory for address 300h ( 768 decimal) as shown here. It is a com mon address for I/O boards and may already be in use in your computer. Verify that it, or the address you choose is available.

Address 300H Shown Below

987654

Figure 2-1. Base Address Switches

SW A9 A8 A7 A6 A5 A4 A3

HEX 200 100 80 40 20 10 8

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3 INTERFACING

The CIO-DAS-TEMP has 32 current inputs desig ned specifically for the AD592 semiconductor-type temperature sensor.

3.1 CONNECTOR DIAGRAM

The CIO-DAS-TEMP employs the 37-pin, D-type signal connector common to many I/O boards. It may be cabled to directly, or throug h a C37FF cable and screw terminal such as the CIO-MINI37.

Signal wires from the AD592 temperature sensors should be connected to the input terminals labeled TEMP0 through TEMP31.

All the power wires should be connected in com mon to the +15V DC power, pin 19.

Please make accurate notes and pay careful attention to wire connections. In a large system, finding a misplaced wire may create hours of work.

+15VDC

TEMP 30

TEMP 28

TEMP 26

TEMP 24

TEMP 22

TEMP 20

TEMP 18

TEMP 16

TEMP 14

TEMP 12

TEMP 10

TEMP 8

TEMP 6

TEMP 4

TEMP 2

TEMP 0

GND

CAL IN

TEMP 31

TEMP 29

TEMP 27

TEMP 25

TEMP 23

TEMP 21

TEMP 19

TEMP 17

TEMP 15

TEMP 13

TEMP 11

TEMP 9

TEMP 7

TEMP 5

TEMP 3

TEMP 1

Figure 3-1. 37-Pin Connector

3.2 CONNECTING THE AD592 SENSORS

The AD592 semiconductor temperature sensor produces a current proportional to tem perature. The sensor employs only two leads, a power lead and the return. The amount of current flowing through the circuit is proportional to temperature and is the signal measured by the CIO-DAS-TEMP.

The AD592 chip has three leads, two of which are used. One is the power and one is the return, the remaining pin is not to be connected and is not used. The power pins from one or all 32 sensors are connected to the +15V (pin 19) of the CIO-DAS-TEMP. The return pin is connected to the TEMP# of the CIO-DAS-TEMP.

VIEW OF SENSOR FROM BOTTOM

WHERE PINS PROTRUDE

IGNAL TO

DAS-TEMP

(-) (+)

Figure 3-2. AD592 Sensor Connections

PIN 2 PIN 1PIN 3

SENSOR POWER

+15V

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Semiconductor temperature sensors may be purchased from some electronics distributors or directly from Measurement Computing Corp. An AD592 potted into a stainless steel probe may be purchased from Measurement Computing Corp. or from other vendors of temperature sensors.

The AD592CN has excellent specifications for ambient temperature measurement (see chapter on specifications).

In addition, because it is a current-output device, the AD592CN is relatively immune to noise pickup and IR drops in the signal leads w hen used remotely. I t is reasonably rugged and will withstand supply irregularities and v ariations or rev ersals up to 20V. Since the A D592s are laser- trimmed, they are interchangeable and have a high initial accuracy that does not degrade over time

Figure 3-3 shows Measurement Computing’s SNSR-AD592-PRB6CN (six inch, CN specifications). T he SNSR-AD592-PRB6CN is composed of an AD592 connected to two lead

TEMP SIGNAL

BLACK

AD592 SENSOR

PIN 2 PIN 1PIN 3

(-) (+)

SENSOR POWER

RED

wires, inserted into a stainless steel probe and potted in place.

The unit is waterproof.

There are two wires protruding from the probe. The RED wire connects to the +15VDC power. The BLACK wire connects to the TEMP# input of the CIO-DAS-TEMP.

SENSOR POWER

RED

SENSOR POWER

RED

AD592 SENSOR IN STAILESS STEEL PROBE

TEMP SIGNAL

BLACK

AD592 SENSOR IN STAILESS STEEL PROBE

TEMP SIGNAL

BLACK

SENSOR AT TIP

Figure 3-3. SNSR-AD592-PRB-6-BN Sensor

4 PROGRAMMING AND APPLICATIONS

Although the CI O-DAS-TEMP is part of the larg er DAS family, there is no correspondence between registers. S oftware written at the reg ister level for the other D AS's will not w ork with the CIO-DAS-TEMP.

PROGRAMMING LANGUAGES The UniversalLibrary program provides complete access to the CIO-DAS-TEMP functions from a range of programming languages; both DOS and Windows. I f you are planning to write prog rams, or would like to run the example programs for V isual Basic or any other language, please refer to the UniversalLibrary manual.

PACKAGED APPLICATION PROGRAMS Many packaged application programs now have drivers for the CIO-DAS-TEMP. I f the package you own does not appear to hav e drivers for the CI O-DAS-TEMP please fax the package name and the rev ision number from the install disk s. We will research the package for you and advise by return fax how to obtain CIO-DAS-TEMP drivers.

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5 THEORY OF OPERATION

5.1 OVERVIEW

The CIO-DAS-TEMP is composed of a C urrent to Voltage (C/V) converter, a Voltage to F requency (V/F) converter, a channel multiplexer, a sensor excitation power supply and control registers (see Figure 5-1).

The temperature signals, connected to the channel multiplexer, are converted from a current to a voltage then from a voltage to a frequency. The frequency is determined by counting pulses from the V/F for a given period. The frequency is use to calculate the temperature.

Sensor Power Supply

AD 31 AD30 AD29 AD28 AD27 ... ... ... AD6 AD5 AD4 AD3 AD2 AD1 AD0

V to F

I to V

32 Channel Multiplexor

V to F Cl ock In

Clock & Pescaler

ISA BUS INTERFACE & CONTROL LOGIC

4MHz

2MHz

Prescaler Out

Figure 5-1. Board Block Diagram

82C54

Counter/Timer Ctrl

CTR 0

V to F Output

Counter

GATE

CTR 1

V to F Pe riod

Counter

GATE

CTR 2

Timer

GATE

Software Trigger

OUT

The C/V converter has an output of 0 to 10 volts, which corresponds to the full scale of the current input or 0 to 500 µA. This input range may be customized at the factory by changing one resistor and one potentiometer. Please call if you have applications requiring up to 0 to 20 mA input.

The V/F converter has an output of 0 to 2 MHz, which corresponds to the full scale of the voltage input of 0 to 10 volts. An AD592 sensor will produce frequency in the range of 992 kHz (−25°C) to 1.512 MHz (105°C). Other sensors such as the AD590 (−55°C to 150°C) may be used as well. The equation for temperature is:

-6

Kelvin = ((10 Volts) * (Fout)) / ((20,000Hz) * (20,000 Ohms) * ( 1 * 10

Amps))

Kelvin = Fout / 4000

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5.2 SIGNAL RESOLUTION AND CONVERSION SPEED

The voltage to frequency converter provides a resolution dependent on the sampling rate. The lower the sampling rate, the hig her the resolution. Sam pling rates may vary from 25 sam ples per second (approximately 16-bit resolution) to 4,000 samples per second (approximately 8-bit resolution). For most temperature measurement applications, rates up to 200 Hz are useful.

The formula for the resolution of the board is:

Full scale range / counts in counter 1

500 µA / (2 <= N <= 65,535 )

The duration of one count is 0.5 µs because the CLK input is 2 MHz

The CIO-DAS-TEMP is constructed of a current-to-voltage front-end and a v oltage-to-frequency converter. T he V/F converter outputs a frequency that is proportional to the v oltage of its input. Resolution increases with sample time since the V/F conversion is an average of the signal over the time of the conversion. The longer the V/F has to settle, the more precise the measurement.

Note that the signal you are measuring should be stable ov er the period of measurement. The CIO-DAS-TEMP is not desig ned for measurement of v ery rapid changes in temperature. For example, the maximum sampling rate for the CIO-DAS-TEMP is 200 samples per second. If your temperatures are changing faster than 200 significant steps per second and you need to precisely trigger and sample that temperature, you have the wrong product and should call technical support to discuss your application.

The CIO-DAS-TEMP is capable of rejecting line noise when the conversion rate is a multiple of the line frequency of the power to the PC power supply. Here are the recommended conversion rates and the accompanying resolutions:

Line FrequencyResolutionRate

60 Hz 0.015 °C*30 Samples/Second

50 Hz0.0125 °C*25 Samples/Second

400 Hz0.1 °C200 Samples/Second

*Note: Exceeds the accuracy of the AD592 sensor.

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5.3 OPERATION OF THE COUNTERS

The 8254 counters 0 and 1 are used to make the frequency measurement of the V/F output. Counter 1 is clocked by the 2 MHz clock source. A value loaded into counter 1 is used to count down to zero thereby providing a precise time interval, known as the gate time. For example, if counter 1 were loaded with the value 5,000 it would count down for 2.5 ms (5,000 / 2,000,000 = 0.0025 sec.).

While counter 1 is counting down, the output pin CTR 1 OUT goes high (a programmable feature implemented in the Universal Library, or your software). This signal is used to gate counter 0.

Counter 0 is used to accumulate counts from the V/F converter. Recall that the V/F converter produces a train of pulses proportional to the voltage on its input. At 0 volts the V/F produces zero Hz and at 10 volts, 2 MHz. If the V/F senses 5 volts on its input, it will output pulses at 1 MHz. If counter 1 has been loaded with a value of 5,000, counter 0 will count pulses for 2.5 ms. 1,000,000 x 0.0025 = 2,500 pulses. Note that the pulses counted from the V/F are exactly ½ the value loaded into counter 1; the time period to count pulses. This is a general rule:

Voltage = 10 x (CTR 1 Load / CTR 0 Counts)

In general, a counter 1 period value of 5,000 is a g ood choice and w ill yield good results. The relationship of degrees Kelvin to counts is:

Kelvin/Count = 500 / Full Scale Count

If the full scale count is 5,000 (as suggested) the relationship is:

500 / 5000 = 0.1K per count

5.4 LINE NOISE REJECTION

V/F converters will reject signal noise that is periodic and of a consistent am plitude because the V/F converter averages the signal. Sinusoidal noise associated with line frequencies is an example. Since the signal is averaged (equal areas over and under the mean cancel each other out) the measurement period must be equal to one cycle, or a multiple of the cycle frequency if noise rejection is desired.

For example, if there is 60 Hz line noise on the signal, the measurement period would have to be:

1/60 = 0.1666

0.16666 x 2,000,000 = 33,333 counts Load this value or a multiple of it into counter 1

For 50 Hz, the calculations are similar. 1/50 x 2,000,000 = 0.02 x 2,000,000 = 40,000

5.4.1 Gate-Time, Resolution and Noise Rejection

The choice of gate time has an affect on the resolution of the measurement, line cycle noise rejection and the rate over which multiple channels can be scanned. Increasing gate time improves both resolution and noise rejection but it will decrease the scanning (multiple channel measurement) rate.

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Generally, the choice of gate time is a matter of factoring the desired resolution against the time the actual measurement takes.

Multiple Channels:

When scanning over multiple channels, the software must explicitly select the next channel in the scan and start a new conversion. Once the next channel is selected, enough time must be allowed for the new channel’s current to propagate through the multiplexers and Current-to-Voltage Converter to settle at the Voltage-to-Frequency converter input. T his is most easily done by doing an extra, or ‘dummy’ conversion, waiting for it to complete and then starting the ‘real’ conversion. Thus, if a gate time of

0.0166 seconds is chosen, the maximum scan rate will be:

Scan Rate = 1 / 2 x [gate time]

= 1 / 2 x [0.0166 seconds]

= 30 samples per second

The following table can be used to select the Gate Count based on either desired maximum sampling rate or desired resolution.

Desire Max Sample

Rate

Required

ResolutionGate TimeGate Count

Line Frequency

Rejection

60Hz0.015 °C0.01 sec33,33330 samples / sec 50Hz0.0125 °C0.02 sec40,00025 samples / sec

400Hz0.1 °C0.0025 sec5,000200 samples / sec

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6 REGISTER MAP

A base address register controls the beg inning, or 'Base Address' of the I /O addresses occupied by the control registers of the CIO-DAS-TEMP. In all, eight addresses are occupied. The registers control the programmable aspects of the CIO-DAS-TEMP performance.

6.1 CONTROL REGISTERS

After a base address has been established, the CIO-DAS-TEMP is controlled by writing to and reading from the control registers. While it is possible to w rite your own control routines for the CIO-DAS-TEMP, routines have been written and are available in Universal Library for DOS and Windows programming languages. Unless you have a specific need to program at the register level, it is recommended that you use the Universal Library or a packaged application program.

Table 5-1. Control Registers

WRITEREADI/O ADDRESS Data Load8254 Counter 0 Data ReadBASE + 0 Data Load8254 Counter 1 Data ReadBASE + 1 Data Load8254 Counter 2 Data ReadBASE + 2 8254 Counter Control8254 StatusBASE + 3 Channel Control & StatusChannel & StatusBASE + 4 ClearInterrupt & Prescaler ControlBASE + 5 ReloadNoneBASE + 6 Counter ControlNoneBASE + 7

The register descriptions include functions of each bit in each 8-bit register as well as some design and use descriptions

BASE + 0 Write - Counter 0 Load Register of the 82C54

01234567