MicroLinks Tech 770 User manual

Microlink 770
Manual
Biodata Limited

Manual Code: 770PDF-1.1
Issue Date: November 2015
Information in this document is subject to change without notice.
Updates are listed on our web site at
http://www.microlink.co.uk/techsupp.html
Biodata Limited 2011http://www.windmill.co.uk/help/http://www.windmill.co.uk/help/http://www.windmill.co.uk/help/
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Table of Contents
1Introduction 1.1
2Installing the Microlink 770 USB Unit 2.1
2.1 Plugging the Microlink 770 into the Computer 2.1
2.2 The Microlink’s Lights 2.1
2.3 Analogue Input Connection Notes 2.2
2.4 Clock and Trigger Connection Notes 2.7
2.5 Specifications 2.9
2.6 The 59x Screw Terminal Units 2.10
3Installing Windmill Software 3.1
3.1 Introduction 3.1
3.2 Installing Windmill Software 3.2
3.3 Configuring Your System 3.3
4Using Windmill with Microlink 770 Hardware 4.1
4.1 Introduction 4.1
4.2 Using SetupIML 4.1
4.3 The Rest of the Windmill Software Suite 4.8
I
Table of Contents

II
Microlink 770 Manual

Introduction
Thank you for purchasing the Microlink 770 High Speed Capture
Package. This Manual tells you:
•About the Microlink 770 unit and how to connect your
signals (Chapter 2)
•How to install the Windmill software (Chapter 3)
•How to use Windmill with the 770 unit
(Chapter 4)
To use the 770 system you need a PC with a USB port. It should be
running Windows 98SE, Windows 2000 or later.
The Microlink 770 unit plugs into the USB (universal serial bus)
socket of your computer. It provides the PC with 16 analogue voltage
inputs, which you can sample up to 100 000 times a second. When
Microlink 59x signal conditioning units are added, you can also use the
770 to monitor thermocouples, current, strain gauge bridges and bal-
anced bridges such as pressure transducers. The 59x units also allow
you to make your connections to screw terminals, rather than to the
37-way D connector.
Here is a brief list of the features of a Microlink 770 system.
•Independent input ranges let you mix different types of
measurements—thermocouples and 4-20 mA process
signals for example–without losing resolution (set with the
SetupIML software module).
•Use the 770 to switch on other equipment simultaneously
with the start of data capture (Section 2.4.4).
•Save data both before and after an event occurs (pre- and
post-trigger data). Useful for seeing, for example, what
happened immediately before a fault. (Set with the
Streamer software module.)
1.1
Introduction

•A digital input into the 770 lets other equipment trigger
data capture (Section 2.4.2).
•Alternatively wait until 1 or 2 readings cross a threshold
before automatically starting to collect data. For example,
when the temperature goes above or below your set
points (set with Streamer).
•Exclude channels from a scan. This lets you use the 770
with different set-ups without having to rewire, and maxi-
mises the speed of data capture. (Set with SetupIML.)
•Set both the interval between reading each channel (ther-
mocouple, strain gauge, etc), and how often all channels
are read. For example, you may choose to wait a millisec-
ond between reading each channel, but after the last
channel has been read pause for 10 seconds before start-
ing again. (Available from both SetupIML and Streamer.)
•For more accurate timing than your computer clock allows,
you can connect an external crystal-controlled clock
(Section 2.4.3).
•All results presented in engineering units: oC, oF, etc (set
with SetupIML).
1.2Introduction
Microlink 770 Manual

Installing the
Microlink 770 USB Unit
This chapter tells you how to connect your signals to the Microlink
770,andaboutthe59xscrewterminalunits.Aftermakingyourconnec-
tions see Chapter 3for details of installing the Windmill software.
2.1 Plugging the Microlink 770 into the
Computer
Plugging the Microlink into your PC could not be easier: just use the
USB cable provided. You don’t have to switch off your computer
first—or even restart Windows.
The Microlink 770 is powered from the USB port. Unless you are
using strain gauges, you don’t need an extra power supply unit.
2.2 The Microlink’s Lights
The Microlink 770 has a green light labelled ENUM and a red light
labelled BUSY. Neither of these will come on until you have installed
the Windmill software.
ENUM ENUM stands for Enumerated. This is lit when the
Microlink has been powered on by the USB plug and
play controller. It is a good indication that the Windmill
USB driver software has been correctly loaded.
BUSY This is lit for the duration of each USB communication. It
is not active until the Microlink has been enumerated.
2.1
Installing the Microlink 770 USB Unit

2.3 Analogue Input Connection Notes
The Microlink 770 provides 16 differential analogue input channels
which you can use to measure voltages. With the addition of 59x units
you can also monitorthermocouples,current, strain gauge bridges and
balanced bridges like pressure transducers.
2.3.1 Differential Inputs
All the inputs are differential: for each input signal there are two sig-
nal wires. The measurement is the difference in voltage between the
two wires. The two signals go into separate high-impedance amplifiers
which monitor the voltage between the input and ground. The outputs
of the two amplifiersare then subtracted to give the difference between
the + and – inputs. For small signals differential inputs are much better
than single-ended inputs. This is because the subtraction of the volt-
ages on each of the input wires means that any voltage common to
both wires is removed, thus reducing noise.
It is important to remember that the voltages at both inputs must be
within the amplifier operating range. A classic error is to connect a bat-
tery between positive and negative inputs with no other connection.
Although the difference between the inputs is well defined, the actual
voltageateachinputcouldbeanything.Connecting one end of the bat-
tery to the 0 V input, either direct or via a resistor, would solve the
problem.
The 0 V of the Microlink 770 is connected to computer earth, which
is usually connected to the mains earth. When making your connec-
tions you should follow this policy.
a. If your signal source is “floating”, i.e. has no reference to mains
earth,then you mustprovide areference by connectingone end of
it to the 0 V input, either direct or via a resistor. The resistor could
have any value up to several MΩ. However large values could
cause 50 Hz problems if your signal source has much leakage to
earth.
2.2Installing the Microlink 770 USB Unit
Microlink 770 ManualAnalogue Input Connection Notes

b. If your signal source is itself earthed then you should connect only
positive and negative inputs. You should make no connection to
Microlink 770 earth.
2.3.2 Input Voltage Range
The Microlink 770 operates correctly with input voltages in the
range ±11 V. The inputs will reject voltages which are common to both
positive and negative inputs. These common mode voltages could be
as big as 10 V.
2.3.3 Maximum Input Voltage
The input multiplexers are protected to 20 volts beyond the power
supply. This means ±35 V if the Microlink is switched on, ±20 V if it is
switched off. When a voltage above the power supply is applied to the
unit, its protection mechanism comes into action and this draws some
current from the signal source. This effect can be a problem when the
computer is switched off as it now draws current from any signal. Extra
series resistors can be added to reduce this fault current. Such resis-
tors will also protect the unit from much higher voltages. However, they
Analogue Input Connection Notes2.3
Installing the Microlink 770 USB Unit
Figure 2.1 For floating signals you need to connect one end
of the signal to the 0 V input on pin 19

willresultinhighernoiseandslowersamplingrates. The extra resistors
can be conveniently housed on a 590 screw terminal unit.
2.3.4 Unconnected Inputs
You can leave unused inputs unconnected, but if you attempt to
read from these unconnected inputs do not expect to get 0 V. They
could be any value. If another connected channel has recently been
read, the unconnected input will return a similar value. This is not
crosstalk. It occurs because the input capacitance of the amplifier is
charged to the voltage of the previous channel and has little incentive
to change when connected to an open circuit.
2.3.5 High Impedance Signals
A similar effect to that described above can occur with high imped-
ance signal sources. When the source is selected it must supply
current to charge the amplifier input capacitance. A high impedance
signal source may take some time to do this so slowing the maximum
sampling rate.
2.3.6 Auxiliary Input
This input has all the facilities of the other sixteen. In Windmill soft-
ware it is reserved for measuring cold junction temperatures with
thermocouples or excitation voltage in bridge circuits. When you use a
593 thermocouple input unit or a 594 bridge input unit, the auxiliary
input is automatically connected as required by the software.
2.3.7 Use with Microlink 593 Thermocouple Input Unit
When used with this unit the auxiliary input is automatically con-
nected to the cold junction sensor. This is an RTD (resistance
temperature device) with 0.8 milliampere flowing through it. If inputs
are unconnected the thermocouple break detection circuitry will cause
them to read positive full scale.
Pins 18 and 37 (–15 V and +15 V) provide a power supply for the
593—don’t connect any other signals to these pins.
2.4Installing the Microlink 770 USB Unit
Microlink 770 ManualAnalogue Input Connection Notes