Isotech microK-400 User manual

User Manual
Applies to:
Software version 1.4.16+
Firmware version 3.17+
Isothermal Technology Limited
Pine Grove
Southport
Merseyside
PR9 9AG
T: [phone]
F: [phone]
E: [email protected]
W: www.microk.co.uk

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CONTENTS
1 INTRODUCTION ...............................................................................6
1.1 Unpacking.............................................................................................................................7
1.2 Safety.....................................................................................................................................7
1.3 Powering Up Your microK .................................................................................................9
1.4 A Quick Tour of Your microK ...........................................................................................9
2 MAKING A MEASUREMENT (TUTORIALS).................................. 12
2.1 Measuring Temperature with a Calibrated SPRT..........................................................12
2.2 Measuring Temperature with a Thermocouple ..............................................................16
3 DRIVING YOUR MICROK............................................................... 20
3.1 Introduction........................................................................................................................20
3.2 The Startup Window .........................................................................................................20
3.3 The Main Window .............................................................................................................21
3.4 The Single Tab....................................................................................................................22
3.5 The Multi Tab ....................................................................................................................25
3.6 The Settings Tab ................................................................................................................26
3.7 The Instrument Tab...........................................................................................................31
3.7.1 Edit Thermometers........................................................................ 31
3.7.2 Edit Resistors ................................................................................ 34
3.7.3 Calibration .................................................................................... 35
3.7.4 Restart Software............................................................................ 35
3.7.5 Update Software............................................................................ 36
3.7.6 Change Password .......................................................................... 36
3.7.7 Port Settings.................................................................................. 37
3.7.8 Set Date and Time......................................................................... 38
3.7.9 Backup Data.................................................................................. 38
3.7.10 Clear Data Files......................................................................... 39
3.7.11 Backup Configuration ............................................................... 39
3.7.12 Load Configuration ................................................................... 39
3.8 Using the Thermometer Database ....................................................................................40
3.9 Using the Reference Resistors Database ..........................................................................41
3.10 Saving Instrument Configurations ..............................................................................41
3.11 Password Protection of Key Settings ...........................................................................42

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4 CONNECTING THERMOMETER SENSORS .................................43
4.1 The “Cable-Pod” Connectors ........................................................................................... 43
4.2 Connecting PRTs (4-wire)................................................................................................. 43
4.3 Connecting PRTs (3-wire)................................................................................................. 44
4.4 Connecting PRTs (2-wire)................................................................................................. 44
4.5 Connecting Thermocouples (external Ice Point or WTP) .............................................. 45
4.6 Connecting Thermocouples (using RJ compensation) ................................................... 46
4.7 Connecting Thermistors.................................................................................................... 46
5 GOOD PRACTICE GUIDELINES.................................................... 48
5.1 Looking After Your microK .............................................................................................48
5.2 Making a Good Electrical Measurement ......................................................................... 48
6 THE MICROK TECHNOLOGY........................................................ 51
6.1 The ADC ............................................................................................................................. 51
6.2 Substitution Topology ....................................................................................................... 53
6.3 Minimising Thermal EMFs .............................................................................................. 55
6.4 Solid-State Switching......................................................................................................... 56
6.5 Inherent Stability............................................................................................................... 56
6.6 Eliminating Self-Heating Effects ...................................................................................... 57
7 CALIBRATION ................................................................................ 58
7.1 Checking Calibration ........................................................................................................ 58
7.1.1 Checking the Master Current Source..............................................58
7.1.2 Resistance Measurements ..............................................................59
7.1.2.1 Zero Ohms Check ..................................................................59
7.1.2.2 400 ΩInternal Reference Resistor..........................................60
7.1.2.3 100 ΩInternal Reference Resistor..........................................61
7.1.2.4 25 ΩInternal Reference Resistor ...........................................61
7.1.2.5 10 ΩInternal Reference Resistor ...........................................61
7.1.2.6 1 ΩInternal Reference Resistor .............................................61
7.1.3 Voltage Measurements ..................................................................62
7.1.3.1 Zero Voltage Offsets..............................................................62
7.1.3.2 Voltage Span Check...............................................................62
7.2 Adjusting Calibration........................................................................................................ 63
7.2.1 Calibrate Master Current Source....................................................64
7.2.2 Calibrating the 400 ΩInternal Reference Resistor .........................65

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7.2.3 Calibrating the 100 ΩInternal Reference Resistor......................... 66
7.2.4 Calibrating the 25 ΩInternal Reference Resistor........................... 66
7.2.5 Calibrating the 10 ΩInternal Reference Resistor........................... 66
7.2.6 Calibrating the 1 ΩInternal Reference Resistor............................. 66
7.2.7 Calibrating Voltage Zeros ............................................................. 67
7.2.8 Calibrating Voltage Span .............................................................. 68
8 RS232 INTERFACE ........................................................................ 70
8.1 Establishing an RS232 Connection...................................................................................70
9 GPIB................................................................................................ 73
9.1 GPIB Address.....................................................................................................................74
9.2 Establishing a GPIB Connection ......................................................................................74
10 SCPI COMMAND SET ....................................................................75
10.1 Command Terminators ................................................................................................75
10.2 SCPI Command Structure ...........................................................................................75
10.2.1 SCPI Numeric Suffices.............................................................. 77
10.2.2 Parameters................................................................................. 77
10.2.3 Units ......................................................................................... 77
10.3 Making Measurements using SCPI Commands .........................................................79
10.3.1 Measuring Resistance using SCPI Commands........................... 79
10.3.2 Measuring Voltage using SCPI Commands ............................... 80
10.4 SCPI Commands ...........................................................................................................81
10.4.1 Command: *IDN? ..................................................................... 82
10.4.2 Command: *RST....................................................................... 82
10.4.3 Command: SENSe:FUNCtion ................................................... 82
10.4.4 Command: SENSe:FUNCtion? ................................................. 82
10.4.5 Command: SENSe:CHANnel.................................................... 83
10.4.6 Command: SENSe:CHANnel? .................................................. 83
10.4.7 Command: SENSe:VOLTage:RANGe ...................................... 83
10.4.8 Command: SENSe:VOLTage:RANGe? .................................... 84
10.4.9 Command: SENSe:FRESistance:REFerence ............................. 84
10.4.10 Command: SENSe:FRESistance:REFerence?............................ 84
10.4.11 Command: SENSe:FRESistance:RANGe.................................. 84
10.4.12 Command: SENSe:FRESistance:RANGe? ................................ 85
10.4.13 Command: SENSe:RATio:REFerence....................................... 85
10.4.14 Command: SENSe:RATio:REFerence?..................................... 85
10.4.15 Command: SENSe:RATio:RANGe ........................................... 86
10.4.16 Command: SENSe:RATio:RANGe? ......................................... 86
10.4.17 Command: INITiate .................................................................. 87
10.4.18 Command: FETCh?................................................................... 87
10.4.19 Command: READ? ................................................................... 87
10.4.20 Command: READ#? ................................................................. 87

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10.4.21 Command: MEASure:VOLTage? ..............................................88
10.4.22 Command: MEASure:FRES:REF? ............................................88
10.4.23 Command: MEASure:RAT:REF?..............................................89
10.4.24 Command: CURRent.................................................................89
10.4.25 Command: TEST:CURRent.......................................................90
10.4.26 Command: CALibrate:CURRent ...............................................90
10.4.27 Command: CALibrate:REFerence .............................................90
10.4.28 Command: CALibrate:REFerence?............................................90
10.4.29 Command: CALibrate:OFFSet...................................................91
10.4.30 Command: CALibrate:OFFSet?.................................................91
10.4.31 Command: CALibrate:GAIN.....................................................91
10.4.32 Command: CALibrate:GAIN? ...................................................92
10.4.33 Command: CALibrate:PASSword .............................................92
10.4.34 Command: CALibrate:UNLock .................................................92
10.4.35 Command: CALibrate:LOCK ....................................................93
11 SPECIFICATION ............................................................................. 94
12 APPROVALS ..................................................................................96
12.1 CE Declaration.............................................................................................................. 96
12.2 FCC Statement.............................................................................................................. 96
12.3 Standards Applied ........................................................................................................ 97

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1 Introduction
The microK-400 and micro-800 are the only precision thermometry instruments
that can achieve sub mK precision and will work with all three common
thermometer sensors (PRTs, Thermocouples and Thermistors). They are based
on a completely new measurement technology, unique to these products, that
provides better accuracy and lower noise than comparables technologies (see
section 6). They are also the first instruments of their type to be completely solid-
state, making them highly reliable.
Despite their sophistication, these instruments are very easy to use. There are no
knobs and dials, just a colour touch screen that makes use of the familiar
Windows CE™ operating system. If you use a Windows™ operating system on
your PC, you will find these instruments intuitive and easy to use. The USB port
on the front panel allows you to plug in and use other devices that work with
Windows CE™ such as a mouse, keyboard or flash drive.
Readings can be displayed in resistance ratio, ohms, volts or temperature units
(°C, °F or K). Algorithms for conversion to temperature include:
PRTs: ITS-90
Callendar-Van Dusen (IEC751 or custom
coefficients)
Thermocouples: IEC584-1 (for type B, E, J, K, N, R, S, T)
Type L polynomial
Gold Platinum Reference Function Polynomial
Thermistor: Steinhart-Hart
This manual provides a comprehensive guide to using the instrument. We
recognise that you will probably not wish to read it through at this time so
suggest you read the safety section below, take one of the tutorials in section 2

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!
and then refer back to the manual using the list of contents to find additional
information as required.
1.1 Unpacking
Your microK product should comprise the following items:
microK precision thermometer
power lead suitable for your country
this user manual
If any item is missing or damaged, please report this immediately to your
supplier. If possible, we recommend that you retain the packaging material in
case you need to return the instrument for calibration or service since it has been
designed to ensure that your microK is properly protected during transportation.
1.2 Safety
The microK is a precision instrument, designed for use in a laboratory. It
complies with the requirements of safety standard EN61010-1 (2001) and is
therefore safe to use in laboratory or light industrial environments. It is not
intended for use outdoors or in extreme environments (refer to specification in
Section 11).
The microK is likely to be connected to thermometer sensors in use and the
operator should take care to ensure that the complete system is safe. For
example, metal sheathed thermometers may be connected to the microK and then
placed in a furnace powered from a 230V electrical supply. Single fault
conditions in such a furnace could lead to the thermometer wires and therefore
the front terminals of the microK becoming electrically live and therefore a
hazard to the operator. Suitable precautions should be taken, such as using an
isolating transformer in the supply to such a furnace. If you require further advice
on safety issues, please contact Isothermal Technology or one of our appointed
distributors - we have extensive experience of thermometry and can provide
advice and equipment to help you.

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Retain these instructions. Use only as specified in these operating instructions or
the intrinsic protection may be impaired.
Please observe the following safety precautions:
Do not use your microK if it is damaged
Only connect to an earthed supply socket. THIS UNIT IS CLASS 1
CONSTRUCTION AND MUST BE EARTHED!
Connect only to a power supply with a voltage corresponding to that on
the rating plate
This equipment is for indoor use and will meet its performance figures
within an ambient temperature range of 5°C to 40°C with maximum
relative humidity of 80% for temperatures up to 31ºC decreasing linearly
to 50% RH at 40ºC
Equipment is for operation at installation category II (transient voltages)
and pollution degree ll in accordance with IEC 664 at altitudes up to 2000
metres
Before replacing a fuse, DISCONNECT THE EQUIPMENT FROM THE
ELECTRICAL SUPPLY
The fuse is contained in the IEC socket on the rear panel. It must only be
replaced with a fuse of the type and rating marked on the rear panel
If a replacement fuse fails immediately, contact your local service agent.
DO NOT replace with a higher value
Always use the power cord supplied. Your sales outlet can provide a lead
suitable for your country
This equipment is for use in moderate climates only. NEVER use the
equipment in damp or wet conditions
Avoid excessive heat, humidity, dust & vibration
Do not place liquid filled containers on the equipment
Do not use where the equipment (or any associated accessories) may be
subjected to dripping or splashing liquids
Ensure that the power switch is easily accessible to allow the unit to be
switched off
The equipment weighs 13kg; use the handles provided. Always
disconnect the equipment from the electrical supply and any ancillary
units before moving
Ensure that tabletop equipment is placed on a solid, level surface, which
is able to support its weight (and that of any attached accessories)
Ensure all cables and wires are routed safely to avoid tripping: also to
avoid sharp bends and pinches
Clean only with a damp cloth. Do not wet or allow moisture to penetrate
the unit. Do not use solvents. See section 5.1 for details of cleaning
procedure
The product should be subjected to regular in-service inspections as
required by local regulations; a yearly interval is suggested
Verify that the supply cordset is undamaged and that the enclosure is
bonded to protective earth. Do not apply earth test currents to any front
panel terminal nor to the shrouds of the USB, RS232 or GPIB connectors

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!
The product is designed to comply with EN 61010-1 and can be flash
tested. It is fitted with radio frequency interference suppressors.
Therefore it is recommended that only a D.C. test be performed.
Performing flash tests repeatedly can damage insulation
This equipment contains no user-serviceable parts. Refer all repairs to
qualified service personnel. Contact Isothermal Technology or one of our
appointed distributors for details of approved service outlets
1.3 Powering Up Your microK
The microK operates on any standard AC electrical supply (88-264V RMS at 47-
63Hz) so unless your supply is unusual you can simply use the power cord
provided to connect your microK to a suitable electrical outlet.
The power switch is located at the rear of the instrument, immediately below the
IEC connector. When you turn your microK on it will go through a standard
Windows CE™ boot sequence and then display a Window containing the
Resume button. Pressing Resume restarts the microK in the configuration it was
in prior to the last power down, you will then see the Main Window and be ready
to operate your instrument.
Before pressing the Resume button, make sure that any thermometers attached
will not be damaged by the sense currents that will be applied (the last values
used). If there is a problem, disconnect your sensors before proceeding and then
reconnect them after changing the sense current to the required values.
1.4 A Quick Tour of Your microK
On the front panel of your microK you will find the input terminals for the three
measurement channels, the touch screen/colour display and a USB connector:

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Input Terminals: The input terminals accept 4mm plugs, spades or bare wires.
The current (I) and voltage sense (V) terminals are spaced on ¾” centres so that
standard BNC to 4mm adaptors (not supplied) can be used to connect to
thermometer sensors that have BNC terminations.
The contact material for the connectors is gold plated tellurium-copper, offering
extremely low thermal EMFs when connected to copper wires/connectors. This
is essential when using precision thermocouples.
Display: The display is a colour TFT VGA (640 x 480) LCD with a long-life
CCFL (cold-cathode fluorescent lamp) backlight. A touch panel is mounted in
front of the display so that you can control the instrument by simply touching the
buttons displayed on the LCD. The touch panel is an industrial grade components
offering good durability. It is intended to be operated with a finger. A stylus
intended for PDAs may also be used – never use a sharp object with the touch
panel as this will lead to premature failure.
The USB Connector: The USB connector is primarily intended to allow you to
connect a USB flash drive, store measurement results and transfer these to a PC.
The flash drive may also be used to backup the databases of thermometers,
reference resistors and instrument configurations for your microK.
USB
Connector
Input
Terminals
Touch Screen
& Display

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Other USB devices such as a mouse, keyboard, keypad or USB hub may be
connected to the USB port and used, provided they utilise the standard class
drivers provided with the Windows CE™ operating system incorporated in your
microK.
On the rear panel of your microK you will find the electrical supply
connector/power switch/fuse module plus the interface connectors that allow you
to connect your instrument to a PC. The RS232 and GPIB ports allow you to
control the instrument and take measurements from a PC with your own software
(see section 8). The command protocol employs the widely used SCPI format
(see section 9 for details). The USB connector is provided for future expansion
and should not be used on this model.
IEC 60320-1
Power Connector
Supply
Fuse
On/Off
Switch
RS232
Connector
USB-B
Connector
(unused)
GPIB
Connector

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2 Making a Measurement (Tutorials)
The operator interface is powered by the Windows CE™ operating system. With
the widespread use of Windows applications on PCs, driving your microK should
be fairly intuitive. As with most Windows™ applications, it is possible to
navigate your way through a process using a number of different paths, so rather
than describe each window and the function of each button and then leaving you
to work out how to operate the instrument, we provide you with a number of
tutorials that illustrate common applications. Even if these do not describe your
application, it is worth working through one of them since it will provide you
with a broad understanding of the wide range of features available on your
microK.
A traditional description of the function of all the features provided by the
operator interface is given in section 3.
2.1 Measuring Temperature with a Calibrated SPRT
From startup, press Resume to restart your microK:

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Before making any measurement, you will have to enter information about the
thermometer into the microK’s database. When the main window opens, press
the Instrument tab:
In the Instrument tab, press Edit Thermometers:
You will be prompted to enter the password (set to “1234” initially, but this
should be changed before using the microK in a real measurement/calibration
application to ensure security – see section 3.7.6). Enter the password to open the
thermometer database window. Press New to create a new thermometer entry in
the database and enter data by pressing the up/down or ellipses buttons by each
field:

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Press Coefficients to open the coefficients window. Press the ellipses buttons to
enter the calibration data for the thermometer from its calibration certificate:
Press OK to close the coefficients window and press OK again to close the
thermometer database window.
Press the Settings tab in the main window and disable channels 2 and 3 (this will
speed up measurements on channel 1, which we will be using) by using the
up/down buttons by the Channel box to select these channels and pressing
Disable. Use the up/down buttons to return to channel 1. Use the up/down (or
ellipses) buttons by each box to select the required settings:

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The sense current is assumed to be 1mA in this tutorial. It can be set to other
values using the ellipses button by the Current mA box (see section 3.6).
Connect the SPRT to channel 1 (see section 4.2 for details on how to connect 4-
wire PRTs). The tutorial assumes you are using the internal 100Ωreference
resistor. To use an external reference resistor, first enter information on the
resistor into the microK’s database (see section 3.7.2), then in the Settings tab
select the channel to which the reference is connected in the Reference Channel
box and the reference resistor entry in the Reference Resistor box.
Press the Single tab to see the measurements in numeric and graphical form. Set
the graph scales manually by making a note of the current Mean value and
pressing Set Scales. This opens the graph scales window. Ensure that autoscaling
is turned off (press Autoscale to toggle autoscaling on/off, the status of
autoscaling is shown by the adjacent indicator). Use the ellipses buttons to set the
y-axis limits to be 0.005°C above and below the current mean value. Use the
radio and up/down buttons to set the x-axis to 5 minutes:

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Press OK to return to the main window. The measurement system will now
accumulate data and after 5 minutes the graph will begin to scroll to show the
last 5 minutes of data:
2.2 Measuring Temperature with a Thermocouple
From startup, press Resume to restart your microK:

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This tutorial describes the use of an uncalibrated type-N thermocouple. The
microK can be used with calibrated thermocouples, in which case you will need
to enter information about the thermometer into the microK’s database and (see
section 3.7.1) and select this thermometer entry from the Thermometer box in the
Settings tab (see later in this tutorial). When the main window opens, press the
Settings tab:
In the Settings tab disable channels 2 and 3 (this will speed up measurements on
channel 1, which we will be using) by using the up/down buttons by the Channel
box to select these channels and pressing Disable. Use the up/down buttons to
return to channel 1. Use the up/down buttons by each box to select the required
settings:

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The reference junction is assumed to be an ice point in this tutorial. It can be set
to the water triple-point or to use a temperature measured by one of the other
channels (see sections 3.6 and 4.6) if using reference junction compensation.
Connect the N-type thermocouple to channel 1 (see section 4.5 for details on how
to connect thermocouples). Press the Single tab to see the measurements in
numeric and graphical form. Set the graph scales manually by making a note of
the current Mean value and pressing Set Scales. This opens the graph scales
window. Ensure that autoscaling is turned off (press Autoscale to toggle
autoscaling on/off, the status of autoscaling is shown by the adjacent indicator).
Use the ellipses buttons to set the y-axis limits to be 0.01°C above and below the
current mean value. Use the radio and up/down buttons to set the x-axis to 5
minutes:

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Press OK to return to the main window. The measurement system will now
accumulate data and after 5 minutes the graph will begin to scroll to show the
last 5 minutes of data:

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3 Driving Your microK
3.1 Introduction
The operator interface for the microK is provided through the touch screen and
colour display. The software is written in Microsoft’s new C# language and runs
under the Windows CE™ operating system. This provides a familiar and easy to
use interface.
The buttons in the microK software have been sized and positioned to allow you
to operate the instrument with your finger. If numeric or alphanumeric data needs
to be entered, a ‘soft’ keyboard window appears. If you are unfamiliar with touch
screen devices such as PDAs, you may initially feel that the touch screen
interface is slow compared with using a mouse and keyboard, but with a little
practice you should quickly become comfortable with the technology and
appreciate its benefits. However, if you prefer to use a USB mouse or keyboard,
you can simply plug these into the USB connector on the front panel. They will
immediately become active provided they use the standard class drivers built into
the Windows CE™ operating system used in the microK. To use more than one
USB device, simply plug a USB hub into the front panel connector.
Calibration data entered into the microK’s database is password protected and
includes recalibration dates (the microK will alert you if you try to use a
thermometer or reference resistor after its recalibration date). This feature
ensures the integrity of your measurements and helps you to comply with the
requirements of accreditation bodies.
3.2 The Startup Window
When power is applied to the microK, it goes through a Windows CE™ boot
sequence that loads the operating system and then starts the microK application.
The Startup Window then appears showing the microK’s model and serial
number together with the version numbers for the measurement system firmware
and microK software used. The window also lists the details of any