Accuracy with
without mercury

The greenlight 300 model has been developed to provide a reliable and accurate alternative to the mercury sphygmomanometer.

It has been designed in the United Kingdom within the NHS for the NHS. The project, which was the result of cooperation between the Freeman Hospital, University of Newcastle and A C Cossor & Son (Surgical) Ltd won a DTI award for Technology Transfer.

The strength of the greenlight 300 is that it is suitable for any patient group (including the pregnant and the elderly) where mercury was used in the past. The reasons for this are as follows:

  • It is a manual device
  • It displays every 2mmHg
  • It is easier to read than mercury
  • It is calibrated to 0.4mmHg
  • It carries out an auto calibration to zero each time it is switched on
  • The cuff deflation rate is displayed
  • Any cuff size can be used
  • Frequent calibration checks are not required

Click the image for a closer view

The UK Medical Devices Directive, in common with most National Regulatory Bodies, requires measuring devices to be checked every year (aneroid devices need to be checked every six months). The specification of the greenlight is that taking into account the worst case tolerance of all components and the range of environmental conditions, only 1 in 10,000 devices would need any form of recalibration each year.

In practice we believed that it would be much better, and experience has now confirmed this enabling us to offer an extended warranty on the calibration. We deliberately chose expensive good quality components to achieve this, as our goal was to give clinical staff assurance that their instrument was accurate and would not need the added expense of frequent recalibration. Extensive pressure cycle tests were carried out to show compliance with the relevant standards.

The greenlight 300 has been validated to the New International Protocol of the European Society of Hypertension by the Mayo Clinic in the United States, giving further independent proof of its accuracy and suitability as a replacement for the mercury instrument. The greenlight 300 is also sold as a test reference manometer for checking aneroid devices – another indication of its reliable accuracy.

For hospital and institutional customers who are planning replacement of their mercury devices we are able to offer trials with the greenlight 300.

The greenlight 300 is available through our network of distributors, and supply or further technical information can be obtained by contacting us or visit