What Particle Counting Reveals
A single total count is rarely enough. Sixty small particles and six large ones can add up to similar totals yet carry very different risk, which is why multiple size channels matter. A fluid particle counter, sometimes listed as a liquid particle size analyzer, reports that distribution, and the distribution is what cleanliness codes and acceptance limits are built on.
The Liquid Particle Counter 70-LPC100 is an 8-channel instrument that uses a semiconductor laser sensor and syringe sampling, with the product page naming oils and other liquids as typical samples.
How Light-Blocking Detection Works
The listing describes the 70-LPC100 as using a photoresist method principle with a semiconductor laser source. In general terms, counters of this kind detect particles by the light they block, and the sequence below shows how a liquid particle counter test runs from sample to result.
- 1
Draw the sample
A syringe pulls a defined volume through the sensor at a steady, set flow rate.
- 2
Pass the cell
The fluid moves through a narrow sensing cell, so particles pass the beam one at a time.
- 3
Cross the beam
A laser illuminates the cell, and a detector measures the transmitted light.
- 4
Register a pulse
A particle blocks part of the light, producing a signal dip that grows with particle size.
- 5
Sort by size
Each pulse is placed into a size channel against a calibration curve.
- 6
Report the counts
Counts per millilitre are shown by channel and can be converted to a cleanliness code.
Calibration matters because the pulse-to-size link depends on it. The listing refers to a built-in threshold-diameter curve and to calibration and verification against standards, which is what ties a pulse height to a stated particle size.
Where Liquid Particle Counting Is Used
Liquid particle counter uses cluster in fields where solid contamination in a fluid has a mechanical or process consequence. The product page lists petroleum, aviation and automotive fields, and names hydraulic oil, petroleum oils, turbine oil, insulating oil and polymer liquids as sample types.
Hydraulic and lubricating oil
A hydraulic oil particle counter checks whether fluid is clean enough for pumps and valves, whose close clearances are damaged by hard particles.
Fuels and aviation
Fuel is checked for solid contamination before and after handling, since filters and injectors are sensitive to particles.
Turbine and insulating oils
Particles in turbine and transformer oils indicate wear and contamination that affect long-term service.
Polymer liquids
Insoluble particles in viscous polymer liquids affect downstream quality, with viscosity limits set by the sensor fitted.
Liquid, Airborne and Regulated Contexts Compared
The wording of a brief often mixes cleanrooms, pharmaceutical manufacturing and water testing, so it helps to separate what each context measures. These are different measurements with different instruments, even where the optical idea is similar.
| Context | Medium | Typical reference | Instrument type |
|---|---|---|---|
| Oil and fuel cleanliness | Liquid | ISO 4406, ASTM D7619 | Liquid particle counter |
| Cleanroom classification | Air | ISO 14644-1 | Airborne particle counter |
| Injectable product particulates | Liquid | USP <788> | Light-obscuration liquid counter, method-specific |
| Water quality | Liquid | Method-specific | Depends on the particle sizes and limits required |
The listed applications for the 70-LPC100 are oils and related liquids, and the page does not describe injectable or drinking water testing, so suitability for those methods should be checked against their requirements. Airborne cleanroom monitoring uses a different instrument, which is why the particle counter category describes laser detection through an air sample. Water testing instruments are collected separately under water testing.
Reading Cleanliness Codes
ISO 4406 condenses channel counts into a short code. The 1999 version reports three numbers, one each for particles of at least 4, 6 and 14 micrometres (calibrated as in ISO 11171), per millilitre of fluid. Each number is a range class, and each step up roughly doubles the allowed count.
| Code number | Particles per mL (typical table values) |
|---|---|
| 13 | 40 to 80 |
| 16 | 320 to 640 |
| 18 | 1,300 to 2,500 |
A code of 18/16/13 therefore means counts fall within those ranges for the three size thresholds. Acceptance limits depend on the equipment and the fluid, so the code is a reporting format rather than a pass mark by itself. These table values are general reference figures and should be confirmed against the current standard.
Sample Handling and Test Practice
A liquid particle count test is only as sound as its sample. Most errors enter before the fluid reaches the instrument.
- Take a representative sample from a flowing, well-mixed point, using clean containers.
- Mix the sample thoroughly before testing, since particles settle in standing fluid.
- Remove air and gas bubbles, as the sensor can count them as particles. Degassing is a common step.
- Dilute samples that exceed the concentration limit. The listing gives a 5 % coincidence error at 10,000 particles per mL.
- Check viscosity against the sensor limit, and dilute thick fluids with a compatible, clean diluent if needed.
- Flush the system between samples and run verification checks on a schedule set by the laboratory.
Specifications Worth Reading Closely
A datasheet for a liquid particle counter instrument rewards slow reading, because several limits interact. The figures below come from the 70-LPC100 listing, which is also summarized in its product catalog.
| Parameter | 70-LPC100 listing | Why it matters |
|---|---|---|
| Measurement range | 1 to 250 µm (25 sensor), 1 to 320 µm (32 sensor), 2 to 400 µm (40 sensor) | Sensor choice sets the largest particle that can be sized |
| Channels | 8, with sizes set from 1 (2) µm up to 100 µm | Defines how finely the size distribution is reported |
| Sensitivity | 1 µm (ISO 4402), 4 µm(c) (ISO 11171, 25 and 32 sensors), 2 µm (ISO 4402, 40 sensor) | The smallest size that can be detected depends on the sensor and calibration basis |
| Sample volume and rate | At least 0.5 mL, 5 to 60 mL/min | Affects how much fluid a test needs and how fast it runs |
| Sampling accuracy | Better than ± 1 % | Concerns the delivered sample volume rather than particle sizing |
| Size discrimination | Below 10 % | Describes how well neighboring sizes are separated |
| Coincidence limit | 10,000 per mL at 5 % error | Above this, two particles can be counted as one |
| Viscosity limit | 100 cps (25), 250 cps (32), 350 cps (40) | Thick fluids need the larger sensor or dilution |
| Pressure and vacuum | Up to 0.6 MPa, vacuum up to 0.08 MPa | Limits for the sampling cabin during pressure or degassing use |
| Interface and display | RS232, LCD touch screen, built-in printer | Determines data handling and reporting |
| Environment and power | 10 to 40 °C, up to 80 % RH, 100 to 245 V, 50 Hz, 80 W | Room conditions and supply must match |
| Size and weight | 220 x 380 x 480 mm, 28 kg | Bench placement and handling |
The listing names ASTM D7619 and ISO 4406:1999, and any requirement to demonstrate conformity to a standard should be confirmed with supporting documents.
Selection Mistakes to Avoid
- Choosing by minimum size alone. Sensitivity depends on the sensor and on how calibration is defined.
- Overlooking viscosity. A thick oil may need the sensor with the higher limit, or dilution.
- Ignoring coincidence limits for heavily contaminated samples, which read low without dilution.
- Assuming that an oil instrument is automatically suitable for injectable or water methods.
- Skipping bubble control, a common cause of falsely high counts.
- Judging liquid particle counter manufacturers on channel count alone. Calibration documentation and service support affect long-term results.
- Treating a liquid particle counter machine as a monitoring tool for room air. Airborne cleanliness needs an airborne counter.
Exploring the Wider Counter Range
This instrument sits within the particle counter group at Lab Expo, part of its analytical equipment range. According to the category page, counters in the group offer multiple size channels, laser detection, touch-screen operation, data logging and portable formats for use from laboratories to field sites.
Within this category, options are usually weighed on the medium measured, size channels, sensitivity, flow handling, data output and portability. The complete Particle Counter category lists the configurations available.