20 nm Liquid Particle Counter: Ultra DI® 20 Plus

Sensitivity range: 20 – 100 nm

Designed specifically for ultrapure water systems, the Ultra DI® 20 Plus liquid particle counter from Particle Measuring Systems (PMS®) quickly obtains statistically meaningful data and will count and size contaminants as small as 20 nmConsistency helps you get more out of your data, even if the instrument moves, so you have more control over your process. The Ultra DI 20 Plus Liquid Particle Counter has a low zero count, large sample volume and high counting efficiency that provides benchmark particle detection. Improved sensitivity allows you to detect process variations more quickly with 20 nm polystyrene latex (PSL) and 9 nm gold (Au).

The UDI-20 is one of Particle Measuring Systems’ “Industry Leading

Read more

Sensitivity” products. This means that there are no products on the market that are more sensitive than these and only PMS offers a line of products covering this many elements of production monitoring. PMS currently leads the market in monitoring performance, sensitivity and reliability in the Ultrapure Water, Chemical and Airborne Molecular Contamination Monitoring fields. PMS’ superior knowledge, technology and service provides High Tech and Chemical manufacturing companies with the most advanced tools to make accurate data-driven decisions, improving both performance and yield. 

Find the best particle counter for your application. 

Download Spec Sheet Request a Quote
Ultra DI 20 Plus
Ultra DI 20 Plus full back
ILS Gallery
PMS Ultra Di 20 Plus back


  • Advanced laser optics and sensors enable detection of particles down to 20 nm (9 nm Au)
  • Unmatched instrument to instrument data stability and matching with thermally stabilized measurements of particles across an 18 to 29°C operating environment
  • Instrument to instrument matching within 20% at concentrations of < 10 particles per ml
  • Compare UPW system performance across multiple fabs in any environmental conditions anywhere in the world
  • Fleet can be swapped without disruptions or questions about the data
  • Two counting modes: 1) High resolution – for pure environments 2) High concentration – for filter challenge tests and lower purity environments
  • Connect directly to PLC and SCADA systems with 4-20 mA and utilize existing network with Ethernet communication
  • Local particle counter data display
  • Larger particle counter sample volumes and ultra-low zero counts detect smaller excursions with more relevant statistical data
  • Uses existing network with ethernet communication
  • Connects directly to PLC and SCADA systems with 4-20mA
  • Compatible with ozonated water
  • Stainless steel housing and dual HEPA filtration for use in clean environments


  • New design eliminates the additional purchase price and maintenance cost for an environmental enclosure
  • Respond immediately to contamination with real-time particle measurement
  • Quickly obtain meaningful statistical data to detect particle excursions and troubleshoot problems
  • Fast sample cleanup shortens the time to move from one sample point to another
  • Speed up analysis time by using shorter sample intervals
  • FacilityNet Software provides more sophisticated process control
  • Set tighter process control limits with low sample-to-sample variation


  • Quantifying particle concentration in state-of-the-art ultra pure water (UPW) systems
  • Filter efficiency measurements
  • Trending analysis at lower particle concentrations
  • Detecting bacterial growth in UPW systems
  • Episodic event tracking and alarming
  • Continuous particle system monitoring
  • Manufacturing process control

Supporting Materials

Specification Sheets

Ultra DI® 20 Liquid Optical Particle Counter >

Ultra DI® 50 Liquid Optical Particle Counter >

FC-200 and FC-100 Flow Controllers >


Submit A Question

Available Accessories

Facility Net

Facility Net

Facility Net Software provides a solution for comprehensive environmental monitoring, including a real-time and historical data display. Compatible with Particle Measuring Systems particle counters and molecular contamination monitors, as well as various third-party products.

Liquid Installation Kit

Liquid Installation Kit

For use with online  applications, the Liquid Installation Kit includes: a Flaretek® flaring tool, five caps, 25 ft of 1/4 in Perfluoroalkoxy alkanes (PFA) tubing and male connectors.

FC-100 FC-200

Downstream Flow Controller

Complete flow control through a liquid particle counter is critical to ensure accurate and actionable data. The Downstream Flow Controllers, FC-200 and FC-100, are the perfect complement to our high precision liquid particle counters.

Bubble Separator Device

Environmental Control Cabinet for Liquid Particle Sensors

The Environmental Control Cabinet for Chem 20TM and Ultra DI® 20 precisely controls the environmental temperature to ensure precise and consistent data. Used inside chemical distribution rooms where the ambient temperature is not well-controlled, the Environmental Control Cabinet shields the particle sensor from environmental changes that adversely impact data quality.


UPW Flow Controllers for PMS Liquid Particle Counters

Precise and continuous control of sampler flow for ultrapure water liquid particle counters.