coming soon Measuring principle The mercury concentration is measured in an optical cell made of fused silica. A maintenance-free membrane pump continuously feeds the sample gas to the optical cell where light absorption measurement takes place at a wavelength of 253.7 nm. This so-called "cold vapor atomic absorption spectroscopy (CVAAS)" measuring method is extremely sensitive for mercury determination and has been used successfully for many years. In contrast to the occasionally propagated atomic fluorescence spectroscopy (AFS) method it is low in interference and requires neither an amalgamation step nor expensive noble gases as carriers. Applications

The VM-3000 Mercury Vapor Monitor serves for continuous measurement of the mercury concentration in gases in laboratory as well as industry and mobile applications. It has a wide variety of applications, such as work place monitoring (threshold limit value), exhaust air monitoring in mercury recovery plants, emission monitoring in the chemical industry, ground air screening of contaminated soil, quality control of hydrogen and natural gas, detector for laboratory applications.

Analytical Performance

The VM-3000 uses a high-frequency driven electrodeless Hg low pressure (EDL) lamp as UV source. It generates emission lines of an extremely narrow bandwidth which are congruent with the absorption lines of the Hg atoms. Cross-sensitivities are thus minimized. The extremely high stability of the UV source in the VM 3000 is a result of the reference beam feedback control method. Total background noise is less than 0.1 µg/m³. To prevent temperature drift both the lamp unit and the detectors are temperature-stabilized. Because the optical cell is heated the VM-3000 is insensitive to water vapor.

Special Features

Metal housing with sturdy handle Option: Rack version with mounting brackets for 19" racks Membrane pump with long service life Input filter with Teflon membrane Stable optical bench Factory-calibrated

Easy to operate

The user controls the VM-3000 by menu-guided inputs via a waterproof membrane keypad. After switch-on the light source is stabilized (approx. 1 - 15 minutes). When the measurement mode is started, a zero adjustment is first carried out automatically. Then the analyzer switches to measurement and continuously indicates the measured mercury concentration of the gas as a numerical value and a graphic bar. The following settings are possible in the "parameters" menu: duration and repeat interval of the zero adjustment, selection of the concentration unit (µg/m3 or ppb), measuring range (0.1-100, 0-1000, 0-2000 µg/m3), input of three different alarm levels, calculation of a mean value over three freely selectable time intervals, printer activation, and, if required, a sample dilution factor.

Display and Output of Measurements

The result of the measurement is displayed on an LCD in real time, both numerically and graphically and is output as an electrical signal of 4-20 mA. The device has outputs for alarm, status and measurement values for full integration in plant control systems. The device also has a serial interface (RS 232) for data collection on a PC.

Self Diagnosis System

If an important component of the VM-3000 malfunctions the user is warned via the display (blinking messages: clean cell, lamp, low battery, alarm) and via output signals.

Battery Operation

For operation independent from mains power the VM-3000 is also available with a built-in rechargable battery and a charger unit. This option allows mobile battery-powered applications of up to approx. 5 hours. Back to Contents

Data Logger Function

A data logger function can be integrated into the VM-3000 as an option. Up to 30000 readings can be stored in the data memory. The logging interval can be set from 1 - 16 seconds revealing a total recording capacity of 4-60 hours. The stored data can be read out with a PC using the serial interface of the VM-3000 according RS232 standard.

VM-3000 Mercury Vapor Monitor Technical Specifications

Measuring principle:  UV-Absorption  Wavelength:  253.7 nm  UV source:  electrodeless low-pressure mercury lamp  Stabilization method:  reference beam feedback lamp control method and thermal stabilization Optical cell:  fused silica (Suprasil), 23 cm long  Optical cell heating:  approx. 50°C  Measuring range:  lowest range: 0.1...100 µg/m³ (0.01-10 ppb) highest range: 0...2000 mg/m³ (0-200 ppb) Sensitivity:  0.1 µg/m³ (0,01 ppb) Response time (99% signal):  < 1 second  Computation of mean value:  automatically via three freely selectable time  Alarm:  when concentration is exceeded, 3 levels programmable  Status alarms:  measuring cell soiled, battery state, UV source  Control pad:  waterproof membrane keypad  Measurement Display:  graphical LC display with background illumination  Signal outputs:  4...20 mA for recorder;  RS 232 bidirectional for PC, data logger etc.;  parallel for printer  Pump:  membrane pump, approx. 2 L / min., optional Flow meter with alarm message  Filter:  PTFE, 1 µ, 47-50 mm diameter  Power Supply:  230 V / 50 Hz (115 V / 60 Hz option)  Battery operation:  external 12 DC source; optional 12 V batteries integrated, ca. 5h capacity  Power consumption:  30 VA   Dimensions:  45 x 15 x 35 cm (WxHxD)  Weight:  approx. 7 kg

Multiplexor operation

A multiplexor unit can be connected for automatic monitoring of multiple measuring points, e.g. as a cellroom monitoring system for chlorine plants. Such a Mercury Monitoring System MMS consists of the Mercury Vapor Monitor VM-3000 , the multiplexor valve unit , the sample bypass pump and two flowmeters. These components are optionally mounted in a industrial grade (IP 65; NEMA 4X) enclosure. Upon demand it can be shielded against magnetic fields.