Instrument Errors - Particle Counter Reports Zero Counts

When the particle counter reports zero counts, it normally means that the LDS sensor is dirty but it will also give zero counts if the sampling syringe does not fill completely and a measurement take place with air and not sample flowing through the sensor.  Following are the reasons the sensor will return zero counts; 

1. Air Gap - The sample syringe is not filled properly and the counter gets zero counts from the “air gap” as the air is pushed through the sensor.
2. Sample Too Dark - The sample was too dark to measure.
3. Contaminated Sensor Window - The sensor windows have become contaminated with a deposit that is insoluble in the systems solvent (Normally cleaning with Citrajet cleaner will solve this problem).
4. Failed Sensor - The laser diode or sensor detector has failed (This is very unlikely).   

Following are corrections for these four (4) common issues; 

1. Air Gap issue

If air is getting into the solvent syringe then there is normally a leak at the inlet port. The “air gap” can be cause by insufficient sample or a sample being too viscous to process. This could happen if the sample does not dissolve in the solvent, the system runs out of solvent during processing or a too viscous sample is processed undiluted. To correct this situation;

1. Remove the tube nut and tubing from the inlet port of the solvent syringe.
2. Check that the flange on the end the tube looks OK. 
3. If the tube flange is OK then re-insert the tube and tighten the nut. NOTE: the tube nut must turn freely when it is being screwed into the valve port and it should only be tightened to a good finger tight. Using a wrench to tighten the nut will destroy the flange and possibly strip the thread on the nut. 

2. Sample Too Dark

Generally, Use less oil and more solvent if the sample appears too dark after a 1:1 dilution.  Pipette in 1 ml of oil and and try running the sample (the system will add 29 ml of solvent).

Generally samples that are too dark to be counted can be diluted at a much higher dilution ratio to generate a count but some caution is needed when processing such samples. Some highly degraded "dark" samples can contaminate the delivery tubing and the cell windows in the sensor. This can result in zero counts on all sample following the dark one and the cell will have to be cleaned thoroughly with heated Citrajet solution to restore normal functionality to the sensor.

If the counts on a highly diluted sample are very high they are likely to contain significant co-incidence errors and a good indication of a co-incidence problem is where high count for the >38um and >70um particles are reported on the diluted sample.

3. Contaminated Sensor Window

Follow the cleaning procedure outlined in the following CINRG document;

Sensor Back-flush Procedure 

4. Failed Sensor

If the suggestions for issues 1 – 3 are carried out and there is still no resolution to the issue, then it is possible that the sensor has failed.  Please contact CINRG support at +1 905 569-8600 x4646 for further support.  In the event that the sensor has failed, CINRG will issue an RMA number and arrange to have a replacement sensor sent out.