Products: Microlink 751-pH - Measuring pH

Measuring pH over USB

Microlink 751-pH measuring

The Microlink 751-pH package comprises the Microlink 751 data acquisition unit, pH signal conditioning, Windmill measurement and control software and lifetime technical support for £895.


Measuring pH with the PC

Just connect your electrodes to the pH box's input protected sockets, plug the box into the Microlink 751 and the Microlink into the computer's USB port. This method of connection means you can use the 751 to monitor, for example, temperatures, flow or level at the same time as pH

The standard pH package handles 12 pH electrodes, but can be expanded to 16 electrodes upon request.

Choose Range and Resolution of pH Measurements

The voltage produced by a change in pH is very small. A change of one pH unit on the pH scale produces (ideally) a change in voltage of 59.16 mV at 25 oC. With the 851-pH package you can choose a narrow input range such as ±10 mV or ±100 mV, or select autoranging to let the software automatically choose the best range for your measurements. Choosing the smallest range that encompasses your signals will optimise the resolution of the measurement.

You can also choose the resolution of the analogue-to-digital converter, selecting 18-bit for more accurate measurements. The higher resolution slows down the system to 6 samples per second, but as pH changes relatively slowly this is not generally a problem. If you need faster measurements, choose 16- or 15-bit resolution.

An integrating analogue-to-digital converter reduces internal noise and a differential amplifier helps reduce external noise.

To further improve accuracy, make sure you keep the wires between the electrodes and the pH box short - spanning not more than a few meters.

Set Alarms on Each pH Probe

You can set two alarm levels on each pH probe, and specify what happens when alarm threshold is crossed. For example, an alarm could be sounded or other equipment switched on.

Data Acquisition Software

Windmill Software is included in the 751-pH package. This modular suite offers data logging, charting, alarm indication, output control and real-time links to other applications like Excel. You can also add process mimic generators, sequence control and many other modules. Should you wish to program the hardware yourself, you can use the IML Tools to do so.

Windmill software: selections are made from dialogue boxes. No programming required.
Make your selections from Windmill software

Free Technical Support and Money-Back Guarantee

All our systems come with free technical support for life and a guarantee that if you aren't satisfied we'll give you your money back.


Dimensions (mm)           180 x 120 x 40
Maximum logging speed     10 scans a second
Memory                    65000 scans
  Operating system          Windows 8, 7 64- and 32-bit
                            Vista, XP, 2000 or 98
  Maximum # inputs          16 differential
  Maximum safe input voltage:
  Power supply on           ±48 V
  Power supply off          ±33 V
  Transient                 ±300 V
  Ranges (V)                ±0.01, ±0.1, ±1, ±10
  Common mode range         ±13 V
  Relative accuracy of ranges:
   gain = 1000               ±0.1%
   gain = 1, 10, 100         ±0.05%
  Analogue to Digital Converter:
  Maximum linearity error   ±0.02%
  Resolution    Integration Time    Samples/Second
  12 bits         2.5 msec          80
  13 bits         5 msec            64
  14 bits        10 msec            48
  15 bits        20 msec            32
  16 bits        40 msec            16
  18 bits       160 msec             6
  Maximum # inputs          32
  Maximum # outputs         32
  (selected through Windmill in ports of 8 lines)
  Power-up state            all inputs
  Compatibility             TTL and 5 V CMOS, can be made 
                            contact closure compatible
  Range                     0 to 5 V
  Output capability         15 LSTLL loads
  Maximum I/O speed         160 channels per second
  Maximum # counters        8
  Resolution                23 bits
  Maximum count (events)    1000000
  Maximum frequency         5 kHz
  Minimum pulse width        500 µseconds
  Frequency gate times      1 or 10 seconds
  Compatibility             TTL, 5 V CMOS, can be made
                            contact closure compatible
  Input voltage range       0 to 5 V

More Information

You can buy the Microlink 751-pH measurement package on-line from Windmill Software. If you need any more details please contact Biodata: e-mail [email protected], telephone: +44 (0)161 834 6688 or tweet @MicrolinkUK. See also our article on How to measure pH for tips on accurate pH monitoring.

Microlink Measurement and Control Systems HomeHome
Data acquisition and control IndexIndex

Measurement News Feed (RSS)
Copyright Biodata Ltd
10 Stocks Street, Manchester, M8 8QG, UK
Tel: +44 161-834 6688
Fax: +44 161-833 2190
Email: [email protected]