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March, 2017

Volume IV, Edition 2

Our Calibrator Certification Service compares and validates the Thermo Scientific™ Model 81i Mercury Calibrator to a National Institute of Standards and Technology (NIST) traceable Vendor Prime. After you have a certified unit in the system, you can maintain calibration in the field. Learn this tip in 5 minutes or less for the Mercury Freedom System:

Five minute calibrator certification tip for the Mercury Freedom System

Utilize the method outlined in the  Advanced Instrument and System Calibrations technical bulletin to calibrate the Mercury Freedom System. The advanced system calibration procedure calibrates the analyzer directly from the calibrator. It has you adjust the PMT voltage and calibrates the analyzer though the Mercury Probe and also adjust the dilution factor.

Key terms and definitions when utilizing the advanced calibration procedure:

Calibration factors

Calibration factors are used to correct the Hg0, Hg2+, and Hgt concentration readings that the instrument generates using its own internal calibration data. The Calibration Factors menu displays the calibration factors.  There are two sets of backgrounds and coefficients. One set is for the instrument and is displayed while in instrument zero or span mode. The other set for system is displayed while in sample, orifice, zero/span, and system zero/span modes. 


The Hg0 and Hgt background corrections are determined during zero calibration. The Hg0 background is the amount of signal read by the instrument while sampling zero air. The background signal is a combination of electrical noise, dark current and scattered light.

Span coefficients

The Hg0, Hg2+, and Hgt span coefficients are usually calculated by the instrument processor during calibration. The span coefficients are used to correct the Hg0, Hg2+, and Hgt readings and normally have a value near 1.000.

Dilution ratio

The Dilution Ratio setting allows the user to view and set the dilution ratio. Typical Dilution ratios with Mercury probes are approximately 40:1  When this value is set, the dilution ratio is applied to the following modes: Sample, Orifice Zero, Orifice Span, System Zero, System Span, and not to: Instrument Zero, Instrument Span modes.

PMT voltage

The PMT Voltage Adjustment screen is used to manually adjust the PMT supply voltage. This screen is visible only when the instrument is in service mode

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Factory repair

Schedule your analyzer, calibrator, probe controller or probe for a Return Material Authorization (RMA) to factory depot repair for complete maintenance and factory specification service.