Trouble-shooting fluctuating measurements.

Some measurement systems, like those monitoring pH, are very sensitive and prone to interference. Small current or voltage surges can cause large fluctuations in readings.

The connections at the back of
Microlink 751 data acquisition unit

Here are some simple tests to follow to determine the cause of the errors. The Microlink 751 multi-function USB unit is taken as an example but many of the tips also apply other systems. Work through the tests one-by-one, eliminating sources of error as you go.

1. Check that the Microlink is working properly. First remove other factors in the system that might be causing the problem, then check the Microlink itself.

(a) Remove any power signal conditioner. This provides surge protection and noise filtering. It should remove interference from other equipment but a faulty one could cause its own problems.
(b) Move the Microlink to another location. If you are using it in a laboratory for example, take it home.
(c) Connect the Microlink to a different laptop running on battery power, not on mains power.
(d) Now you can test whether the Microlink is the source of the noisy, fluctuating, data. Connect together the first positive input pin, the first negative input pin and the 0 V input pin. With the Microlink 751 these inputs are on pins 20, 1 and 19. You could use paperclips to connect the three pins. Leave all other inputs unconnected.

The Microlink is now shorted out: if it is working correctly it will produce a reading of zero. If not the fault lies with the unit and Technical Support should be contacted and the unit returned. If the reading is zero then the problem is very unlikely to be caused by the Microlink and you can go on to step 2.

2. Once the DAQ unit has been eliminated as the source of the fault, the power supply to the computer should be tested. Plug the laptop into the mains - the reading should still be zero.

3. Reconnect any power signal conditioner. Again, check that the reading is zero.

4. The sensors should be tested one-by-one. For example, place a pH probe in a known solution and see if the reading is as expected. Keeping the signal wires short and far away from electrical machinery helps reduce noise. The electrodes may also require cleaning. electrodes.

5. Move everything back to the original location. If the readings become erratic go through the tests again.

6. Disconnect from the laptop and connect to the original computer. Again, if you now get noisy readings repeat the tests. 7. Finally make the measurements in a real situation.

Discovering at which stage the problem occurs will allows the identification of the source and the taking of remedial action.

@DataAcquisition #PAuto #Calibration

Data acquisition software now works with even more devices

Windmill Software are pleased to launch a major new improved version of ComDebug, the free serial communication, data logging and trouble-shooting software.

The improvements were all suggested by users of ComDebug, and make the software even more versatile. For instance, with ComDebug users can now:

- Log data from sensors that send data as a web page
- Collect data as 4-byte (32-bit) integers, 4-byte words (double words), ASCII characters, hexadecimal, signed bytes, bytes, bits, 4-byte floating point or 4-byte reverse floating point
- Enter custom commands to extract data or output control messages
- Easily identify communication problems
- Communicate more easily with TCP/IP, Modbus, RS-485, RS-422 and RS-232 measurement devices

The new custom commands allow ComDebug to extract data even if it is an unusual format. For example, the start of a message from a measuring device might be indicated by only part of a byte whilst the rest of the byte carries data. By entering a custom command, ComDebug can log the
just data and ignore the rest. Users can enter custom commands themselves, or Windmill Software is happy to set up a custom command for any instrument.

Another improvement makes it easier to use ComDebug with some Modbus devices. Previously ComDebug read data as 2-byte words. This was inconvenient when the device sent 4-byte words. One user had to open the log file in Excel, concatenate the two hex strings then convert the hex
to decimal. Do-able but laborious. Windmill Software have taken notice of his "gotta be an easier way???" plea and added options to collect data as 4-byte words or 32-bit integers.

The new software also now has a trouble-shooting screen, so users can see exactly what is being sent to and received from instruments, and identify where any problems may be occurring. The screen shows the outcome of each data reading, the messages sent and received, the data extraction procedure and result, and the time in hundredths of a second since data logging started.

ComDebug communicates with a vast range of instruments over TCP/IP, Modbus, RS-485, RS-422 and RS-232. These include dial gauges, digital indicators, digital thermometers, force gauges, I2C devices, load meters, multimeters, PIC microcontrollers, plcs, pressure transmitters and power analysers, from manufacturers like Fluke, Garmin, Honeywell, Love Controls, Mettler Toledo, Motorola, Omron, Rockwell Automation, Siemens and Texas Instruments.

Monitor strain gauges over the internet!

Windmill Software have launched the Microlink 851-SG Strain Data Logger, which logs data from strain gauges over internet or Ethernet. It can be used as a stand-alone data logger, or for real-time data acquisition on a PC.

As well as strain, the data logger can monitor pressure transducers, voltage signals and digital inputs, count; control digital outputs and count up to 1 million events. With extra hardware it can also measure temperature, flow, level, and other signals.

Windmill software makes the package very easy-to-use: no programming is required. Automatic ranging lets the software match the strain signal as closely as possible. Users can also select the resolution of the A-D converter from 12- to 18-bits: choose between high resolution and high speed.

Two alarms can be set on each signal input, again through the Windmill software.

Strain measurements are returned in microstrain, or in the engineering units of your choice.

They offer free technical support for life and money-back guarantee if not satisfied.

The 851-SG package can monitor strain gauge bridges and balanced bridges such as pressure transducers. It enables configuring individual channels to accept any of these inputs:

- voltage - quarter bridge: single strain gauge

- half bridge: tensile + compressive strain gauge

- half bridge: normal + transverse strain gauge

- full bridge: 2 tensile + 2 compressive gauges

- full bridge: 2 normal + 2 transverse gauges

- full bridge: tensile normal + compressive normal + tensile transverse + compressive transverse gauge

Strain gauges need an external excitation voltage to supply sufficient current to keep all the bridge circuits energised. The 851-SG package provides four sets of 16 screw terminals giving + and - excitation and signals for each of 16 bridges. Two 1 kOhm termination resistors are mounted in half bridge configuration whilst high quality 350 and 120 Ohm resistors can be provided for the completion of quarter bridges.

When a bridge input is selected the Windmill software monitors excitation voltage and performs the bridge calculation to produce a reading in microstrain. This eliminates errors due to changes in excitation voltage.

The initial unstrained bridge measurement is often much larger than the change in signal due to strain. If this initial value is not accounted for, it restricts the resolution you can obtain - i.e. the smallest signal you can measure. Windmill software can zero or balance the bridge, nulling the offset of the initial voltage. So instead of measuring over a wide range, 0 to 0.5 V for example, you can choose a narrow range such as 0 to 0.01 V.

Each range is divided into a fixed number of steps: the resolution. The smaller the range and the larger the resolution, the more precise the reading. The 751-SG offers a choice of resolutions from 12-bit for fast sampling to 18-bit for greater precision.

Excel as a data logger!

Windmill Software has announced new software for easy data logging and control with Excel. Called Windmill Real Time Data, it lets an Excel spreadsheet collect readings from sensors and instruments over USB, Internet, Ethernet, Modbus, RS-485, RS-422, RS-232 and TCP-IP. It also enables users to control devices and output channels from Excel.

The software allows Excel to act when data readings cross an alarm threshold: automatically switching equipment on for example.

Users can choose how often to read data from devices and how often to update the data in Excel. Being able to set differing rates for reading and updating data is useful, for example, for showing average readings over time. All readings are timestamped, with the time each reading was taken being recorded in an adjacent column.

The Windmill Real Time Data software makes data collection with Excel both easy and robust. Once the software is installed, users simply enter a formula in a cell - or a line in a macro - and Excel turns into a data logger.

The software runs under Windows 8 and earlier versions of Windows. It is available for just 117 Euro, or 58 Euro for existing users of Windmill. The price includes free technical support for life.

New suite of data acquisition and control programs

Windmill Software has launched their Enhanced Windmill software suite. Enhanced Windmill includes human machine interface software, data logging, charting, output control, programming tools, alarm monitoring and drivers for instruments communicating over Ethernet, Internet, USB, Modbus, RS232, RS422, RS485 and TCP/IP.

Enhanced Windmill runs under Windows 8 and earlier versions of Windows. The package is available for just Euro 345 and the company offers free technical support for life.

The human machine interface software, called Graphics, makes it extremely quick and easy for users to create virtual instruments, process mimics, annunciator panels, wiring diagrams or any display they choose.

Windmill Logger includes alarm indication, logging to a new data file at regular intervals, logging only when new data arrives and many other options. All logged data is time stamped and data can be sent to Excel and other programs in real-time.

No programming is required to use the Windmill Software, but "IML Tools" are included for those who do wish to write their own programs. These take care of all the hardware tasks, leaving users free to concentrate on their applications which can be re-used with different instruments and devices. Amongst other things, the Tools can quickly configure the hardware, take input readings and write to analogue and digital output channels. They comprise an Active X control for Visual Basic, Javascript, Excel and so on.

Other programs in Enhanced Windmill include alarm monitoring and handling, charting, data replay and sequence control.

Automating M&C tasks

Windmill Software has  a major new version of its Test Sequence software. Test Sequence automates measurement and control tasks by running a text file of commands. No programming knowledge is required.

The new version adds many new commands, making Test Sequence even more powerful. For example, it can now loop several times through a command sequence; check if a condition is true and act accordingly; wait until a specified amount of data has been collected; show instructions to a user and let a user manually adjust analogue outputs.

Test Sequence understands a total of 47 commands, all specifically for data acquisition and control. Combining these commands lets Test Sequence, for example, perform PID (proportional-integral-derivative) control; watch for alarms and take appropriate action; send key-presses to other Windows programs like Excel; start and stop data logging according to conditions or time of day; change the speed of sampling when alarm thresholds are crossed and ramp values up and down over time.

Test Sequence runs under Windows 7, Vista, XP, 98 and 95. It requires a Windmill 7 hardware driver which lets Test Sequence work with almost any RS-232, RS-422, RS-485 or Modbus device. Test Sequence also handles USB and Ethernet hardware. The new version of Test Sequence is currently reduced to 60 Euro. 

Data acquisition software for Windows 7

Windmill Software's new data acquisition software suite for Windows 7 64- and 32-bit, Vista and XP.

Windmill 7 software lets users read and control up to ten devices over RS232, RS422, RS485 and Modbus. The software comprises ready-to-run applications to chart and log data, control analogue and digital outputs, monitor the com port and send data directly to Excel.

The new software is offered  at an introductory price of £50 (60 Euros or $80) - a 65% discount on older versions of the software. Technical support for life is included in the price, and there is a money-back guarantee if the software doesn't live up to expectations.

Windmill works with instruments communicating with ASCII or binary messages. With a flexible approach to extracting data values, it is suitable for collecting readings from the majority of serial instruments which can be plugged into the computer's com port. These include PICs, power meters, digital indicators, multimeters, data loggers, GPS receivers, gyro compasses, motion sensors, gas analysers, pH transmitters, particle analysers and laboratory scales.

Users have the freedom to mix and match equipment from many different manufacturers in many combinations. For example, serial devices from A&D, Bruël & Kjær, Dataq Instruments, Datel, Datataker, Denver, Garmin, Mettler Toledo, Microchip Technology, Motorola, Molyteck, Newmar, Nu-Metrics, Omnistar, Omron, Orion, Parallax, Sartorius, Siemens and Texas Instruments have all been handled by Windmill. Many channels of data can be accepted from each instrument.

Also included in the package is a program to monitor com port communications. This lets users see all bytes sent and received, even non-printing characters like carriage returns. This is crucial when dealing
with binary data. Called ComDebug, the software also shows the state of the input and output lines to the computer's com port.