Model 421-HMI


  • Color touch-screen interface
  • Modular configuration is highly customizable
  • Wide measurement range up to 6.5 decades, dual or quad ion chambers for gamma compensation
  • Select ion chamber size: dual 2L or quad 2L
  • Upgraded alarm system: two adjustable tritium level alarms, latching and non-latching alarm modes, malfunction and low flow alarms, and up to 3 alarm relays (two level, one malfunction)
  • Visual and audible alarm indicators
  • Alpha pulse suppression, radon rejection
  • Long-term zero stable, span calibration is permanently stable due to special electrometer design
  • Remote mounting of ionization chamber (25 feet standard)
  • Ethernet output
  • Optional totalizer for computing total tritium release in Ci or Bq


The Model 421-HMI is based on the Model 421 but includes an integrated computer and color touch-screen display HMI instead of the standard digital panel meter display.  The color-touch screen HMI handles all control (alarm set-points, measurement units), alarm indicator, and display functions.  Includes Ethernet output, low flow alarm, and malfunction alarm indicators (low voltage failure, high voltage failure, or electrometer failure).

The Model 421-HMI features a wide measurement range of up to 6.5 decades with dual or quad ionization chambers for gamma compensation.  Useful for accurately measuring low levels of tritium even in areas with an elevated gamma background.  The Model 421-HMI is part of our modular series, designed for easy customization, and features an upgraded alarm system that includes two adjustable tritium level alarms (alert level and high level) with audible and visual alarm indicators, low flow alarm, malfunction alarm (low voltage failure, high voltage failure, or electrometer failure), acknowledge (mute), latching or non-latching alarm modes, and up to three alarm relays (two level relays and one malfunction relay).

The Model 421-HMI typically supports two different chamber sizes, depending on your range and sensitivity requirements, select either dual 2L chambers or quad 2L chambers.  Quad 2L ionization chamber assembly arranged in a cruciform geometry provides the best sensitivity, stability, and omnidirectional gamma compensation.  Ionization chambers can be mounted remotely (up to 25 feet standard), or locally inside the electronics enclosure.

Typical Measurement Ranges:

Ci Bq
Dual 2L:  1 to 199,999 µCi/m3 0.01 to 1,999.9 MBq/m3
Quad 2L: 0.1 to 19,999 µCi/m3 0.01 to 1,999.9 MBq/m3

A wide variety of options are available, including: choice of additional second data output (RS-232, RS-485, 4-20mA), pump type and flowmeter assembly, remote display unit, helium leak testing, wire-grid ionization chambers, gold-plated measurement chamber, HTO only measurement (noble gas compensation), and more.

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