Portable particle counter tattles on dirty oil

The opto-mechanical LaserCM particle counter features a continuous wave, single-point source laser. Automatic Particle Counters (APC’s) have been widely used for many years to monitor the condition of hydraulic fluids. However, only recently have APCs become flexible enough to leave the lab and work on-line and produce credible and accurate results. The LaserCM and several versions of it were developed by Parker Hannifin’s

The LaserCM portable particle counter features microprocessor controlled optical scanning for accurate contaminant measurements with a calibration range from ISO 7 to ISO 22 without counter saturation.

hydraulic filter division in the U.K.

The most common monitoring technique used in APC’s is that of light obscuration or light blockage. The LaserCM works like this:

Particles are measured by a photo diode that converts light intensity to a voltage output which is recorded against time. As the particle moves across the window the amount of laser light lost is proportional to the size of the particle. This reduction in voltage is measured and recorded. This voltage loss relates directly to the area of the particle measured, is changed into a positive voltage and then in turn changed into a capacitance value. This value is counted and stored in the LaserCM computer in one of 6 channels according to particle size.

Readouts are displayed on the hand-held LCD in the accepted ISO and NAS standards ready for hard copy printing or RS232 computer download. The on-board computer allows storage of up to 300 test results.

On-line APC’s must be able to test oil samples however delivered to the machine. Parker Hannifin U.K. Ltd. had to develop a way to ensure the on-line APC could test a sample without diluting it, a conventional laboratory technique, and a difficult practice for a portable unit. By careful design and window sizing, the unit measures gravimetric levels up to 310 mg of dirt/litre, (equivalent to up to 4 million particles >5 micron per 100 ml), without making the instrument susceptible to counter saturation.

Other features include:

• Instant, accurate results are available after a 2 minute test cycle.
• Data entry allows individual equipment footprint record
• Data graphing selectable via the integral printer
• Auto 300-test cycle logging via LCD handset input.
• RS232 serial port computer interface.
• Limit level output to control peripheral equipment such as off-line filtration via internal relay limit switches.
• Auto-testing allows conducting automatic sequencing tests on flushing systems, for example.
• Bar code swipe wand allows handset data loading.
• Worldwide service and technical support.