Cheap and so effective. These have to be one of my favourite instruments! In times gone-by I often struggled to check the fan/motor direction to ensure that the phases had been correctly connected …. now it is so simple – with no need for physical contact with the motor, fan or wiring!!
Remember – around 8% of centrifugal fans in the UK are apparently running backwards (!) …. and importantly, when operating in reverse ….. they do still draw air in the correct direction (but only at about 40-60% of design flow)!!
An essential part of every TExT examination is to physically check that the fan is actually turning in the correct direction.
Simply lay the PM5900 along the axis of the fan motor, align the instrument with the shaft outlet from the fan motor as shown in the pictogram in the centre of the instrument (see above), hold in line with the motor (up to about 80mm above and parallel to the motor) – press the button …. and the rotational direction is indicated as ‘left’ or ‘right’ by the illuminated lights.. No need to attach cables/leads.
The test leads supplied can also be used to determine motor rotation on synchronous and asynchronous 3 phase motors.