Mercury VM-3000

The VM-3000 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. 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.

Figure: Schematic flow diagram of VM-3000 Mercury Vapor Monitor

The VM-3000 uses a high-frequency driven electrodeless Hg low pressure (EDL) lamp as UV source. It generates mission 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. The VM-3000 is insensitive to water vapor thanks to the heated optical cell.

 

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 easily replaceable teflon membrane

Stable optical bench

Automatic zero calibration

 

Factory-calibrated- no need for frequent recalibration (short term factory recalibration service available)

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.

 

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.

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 signal output..

 

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

 

A data logger function can be integrated into the VM-3000 as an option.
Up to 15000 readings can be stored in the data memory. The logging interval can be set from 1 - 999 seconds revealing a total recording capacity of + 100 days. The stored data can be read out with a PC using a serial connection cable according RS232 standard. 

Ankersmid M&C bvba,         Neerlandweg 21, B-2610 Wilrijk,        :  info@ankersmid-mc.be,  : (32) - 3/820 80 01,