cHFM Compact Hand & Foot Monitor

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Basic System Components

The cHFM is a complete contamination monitoring system comprised of three independently mounted components; the electronics assembly comprised of the electronics enclosure and one or more SDB (Simple Detector Board) modules, the hand monitor assembly, and the foot monitor assembly. The system includes all necessary cables and tubing to connect

the three assemblies.  An internal battery provides for

8-hours continuous operation away from AC power.

 

Electronic Assembly

The electronics assembly provides the user interface

and all necessary detector support electronics.  It

consists of an aluminum dust-tight and splash-proof

enclosure containing a Windows-CE 5.0 processor board along with internal counting logic coupled to the detectors via the rear panel mounted SDB detector interface modules.  It is removable from the wall mount bracket without tools and uses quick-release cables and gas connectors from the detectors to allow the electronics assembly to be easily detached from the mounting bracket for maintenance.

 

The front panel includes all indicators and controls. The LCD touchscreen display is used for

system configuration as well as to display counting results. Front-panel mounted LEDs are

used for status indication; the Alarm LED (Red) indicates that contamination was detected, the Ready LED (Green) indicates the monitor is ready to perform a count, the Out of Service LED (Yellow) indicates a trouble condition and that the monitor cannot be used.  Two Rotameters are also mounted to the front panel to provide inlet gas flow adjustment, and to indicate outlet gas flow.  The audible Sonalert™ alarm sounds when contamination is detected and is

cHFM alpha beta particulate surface monitor for hands or feet or frisker-use via P-10 gas proportional detectors

The Bladewerx cHFM™ is a space saving alpha/beta contamination monitor configurable with up to four gas-flow proportional detectors -- a combination of hand, foot, or frisker detectors . The modularity and small footprint (less than 2.5ft²) provides excellent versatility and allows for wall mounting, cart mounting, or table top use. The cHFM is compact, easy to setup, and user friendly, making it highly efficient for personnel monitoring in high traffic applications.

 

The cHFM performs counting and alarming in frisker ratemeter mode when the hand-held frisker probe is being used and in fixed count time mode when monitoring hands and feet. Each detector has its own user settable parameters and alpha and beta measurements are individually analyzed and displayed. The software also provides automatic background compensation with statistical monitoring for abrupt changes in ambient gamma level.

cHFM Cart-Mount option pictured here

Hand-Foot monitor e-box face with gas inlet and outlet controls, LED indicators, LCD, sonalert, and buttons for alarm acknowledge and count now.

silenced/reset by pressing the Alarm Acknowledge pushbutton. For counting small articles on the hand detector, a Count pushbutton is provided to manually start a count cycle, thereby over-riding the photoelectric sensors.

 

The power On/Off button is located on the side panel along with the USB port for downloading log data. The click rate speaker driven by the frisker probe is also located on the right side.  The rear panel of the electronics assembly includes the 12 VDC charger/ power connector, P-10 gas quick-release connectors, and the Ethernet connector. The detector electronics SDB modules are mounted externally to the rear panel and provide the interface between the data processing computer and the gas proportional detectors.  The SDB modules (one per detector) are easily removable without tools.

 

Hand & Foot Monitors

The wall mount for the hand monitor and electronics assembly is designed so that the LCD display can be positioned at an adjustable height with respect to the hand monitor so that a comfortable hand position is not compromised by the display height.  The foot detector

cHFM user interface with alarm settings for alpha and beta readings, beta background, and frisker background.

assembly can be conveniently placed on the floor or on a cart below the wall mount and allows for an adjustable angle of from 15° to 30° for comfortable foot placement. Both hand and foot monitor assemblies are equipped with 24 cm x 39 cm (9”x15”) gas proportional detectors with MHV connectors for high voltage and signal plus a quick-disconnect connector for the P-10 counting gas.  The hand and foot monitors use photoelectric sensors to trigger the count cycle when a user places their hand or foot on the surface of the detector assembly.

Frisker Probe

The gas proportional frisker has a nominal 100 cm² sensitive area and includes an MHV connector, which supports high voltage, signal, and counting gas flow.  It is attached to the wall mount bracket along with the hand detector and electronic assembly.  When the frisker is removed from the mounting bracket a micro switch automatically activates frisker counting mode.

 

Alarm Indications and Remote Monitoring

Contamination levels and status changes are annunciated on the display, the status LEDs, and audibly via the Sonalert.  When the net detector count rate exceeds the user defined alarm level, the alarm condition is indicated by displaying the net detector reading on a color-coded background (red = alarmed,   yellow = out of service, green = normal). With the 802.11 Ethernet connection, the cHFM reports status and readings to a local network running Bladewerx RadNet software or other RadNet-compliant client software.

 

Data Logging

The cHFM creates log files every time a user does a count.  The log files are stored locally as text files and may be copied to a flash drive inserted into the built-in USB port.  Log data files are saved in a Microsoft Excel-compatible “comma-delimited text” format.

Functional Highlights

 

•  The cHFM regularly checks for changes in background by comparing each new background count to the average background rate.  If the change exceeds the user selectable sigma factor, the cHFM goes “out of service” until it determines a new background average.

 

•  Alpha and beta net count rates are determined for each channel by subtracting the current average background rate from the gross count rate measured during the fixed count time.

 

•  Individual alpha and beta alarms can be user set for each detector channel.

 

•  Detector efficiencies determined during calibration are stored and used to display contamination levels in dpm (large area sources recommended for calibration)

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