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RFM900
Automatic Digital Refractometers

Robust Manufacture:
Construction materials have been carefully selected to withstand common samples and solvents. The chemical resistant Polyurethane Foam case offers a seal against moisture and corrosion, whilst materials in contact with the artificial sapphire prism are of the highest specification including Kalrez® gaskets and PEEK spill barriers as standard.

Unlike many manufacturers that use external heatsinks, the RFM900 temperature control system comprises internal elements to prevent samples from covering and therefore insulating heatsinks. Pulse controlled airflow through filtered ducting ensures there is no contamination to the optics, electronics or heatsinks.

Optional Harsh Environment Protection includes special filter pods and vent exit covers that stop samples seeping into the aforementioned ducting. Optional keypad covers and waterproof power supplies (IP66) are also available, allowing use of the ensuring performance year after year and in the worst of conditions!

Installation Wizard:
RFM900 refractometers are factory set to operate in refractive index mode at 20ºC and in English language. After purchase, the instrument runs an installation wizard on start up that helps users configure the instrument. Parameters include language, date/time, scale, temperature, security and RFID tag allocation.

After installation, the installation wizard may be accessed via the instrument menu.

Measurement Features:
RFM900 series refractometers offer one of the highest measurement specifications available. Results may be displayed in refractive index or Brix. Alternatively, over 15 industry standard scales may be loaded from the instrument library without the need for expensive and fragile ‘plug-in cards’. Customer defined scales may also be created using software available free of charge from this site, so creating special scales to display a particular chemical % concentration is never a problem.

Sample containment is vital in providing a rapid temperature response. A carefully shaped “easy clean prism dish” ensures only the right amount of sample is applied to the sapphire prism, optimising temperature stabilisation time. Carefully placed temperature sensors ensure rapid response so that two internal Peltier devices quickly control the sample temperature. Even the airflow to the Peltiers is considered to ensure maximum performance. When in ‘SMART temperature stability mode’, the refractive index or other scaled result is only displayed when both reading and temperature has stabilised. ICUMSA temperature compensation is also provided with the option to load User Temperature Compensation to correct to any specified reference temperature.

Sample Cover ‘Read’ Function:
RFM900 instruments feature a lightweight, non-contact sample cover that prevents ambient light entering the optics. The instrument may also be programmed so that replacement of the cover instigates a reading, negating the need to press the read button.

User Interfaces:
RFM900 refractometers have a back lit ‘blue light’ LCD dot matrix screen that can be inverted to show two display styles, with legend available in a choice of at least four different languages¹.

A powerful microprocessor lies behind the simple ‘telephone style’ keypad providing standard measurement or industry specific METHODS. The reading display can be configured to show one or a number of different measurement parameters along with instrument configuration, batch code and operator identifiers in accordance with GLP and the technical requirements of FDA regulation 21 CFR Part 11.

Navigation is by cursor or numeric index with access protected to three levels (low/medium/high) depending on the security of measurement required. Users may be specifically defined, controlling access to specific levels or the entire instrument menu. After a specified period of instrument inactivity, the software will ‘time-out,’ requiring further user identification. Authorised use of the instrument is therefore protected by keypad PIN entry or by way of RFID tag.

In low or medium security levels, the RFM900 can store up to 700 results that can be displayed in tabular form on the instrument display. Results may even be sorted by user or date as required. Alternatively the stored data, along and a configuration file that logs all changes made to the instrument set-up, may be extracted to PC by special Data Acquisition software forming an audit trail. This software is available free of charge from the download section of this website.

Readings may also be simultaneously output to a printer and/or sent to LIMS in CSV format. An Excel workbook that enables reading data to be collected directly into Excel, is available from the downloaded section of this website. 

One other important feature is that statistical measurement in accordance with USP may be obtained by a simple print function. Five random samples from a single batch may be applied at a specified interval, measured, removed and the prism cleaned with the MEAN subsequently reported as part of a single experiment.

Radio Frequency Identity (RFID):
Uniquely, rapid identification of users is processed in the RFM900 by a simple radio receiver at the front of the instrument. Three* tags are supplied with the instrument that can be programmed in accordance with the level of access granted to any named user as part of the installation wizard or set-up menu. Up to 50 users may be assigned with different access rights. Functions such as measurement, calibration and configuration is then only granted when the tag is swiped across and the user recognised. 

Manipulation of stored data may also be simplified by use of RFID.

* further tags in packs of 3 or 10 are available as optional extras

Methods:
Under normal operation, the methods system offers a rapid means of configuring instrument parameters between readings such as setting the scale, temperature compensation type and  operating temperature as well as making comparison to method specific reading limits.  In addition to this feature, the RFM900 series refractometers are pre-programmed with a number of industry standard methods to assist in other operations. These include methods for the calculating regionally adjusted coffee solids (%TS) when compared to dried methods including daily or batch offset functions, offsets for comparison to other methods such as RI vs. oven solids and calculation of carbon type composition of mineral insulating oils in accordance with ASTM D 2140.

Security Features -
FDA Regulation 21 CFR Part 11:
Strict controls within the pharmaceutical industry dictate the need for high levels of security in terms of sample analysis and data control. Instrument software facilitates the level of security: low, medium and high. The lowest level requires a 3-digit PIN to access determinable parts of the instrument menu, whilst ‘medium’ requires an 8-digit PIN. In either of these modes, setting the supervisor PIN to zero allows free access to all users.

The highest standard of security is compliant with the technical requirements of FDA regulation 21 CFR Part 11, where access to measurement and data transfer is strictly controlled, making use of extended passwords and electronic signatures that have a controlled schedule of validity and re-usage. Changes to the instrument configuration are also recorded in the instrument as an ‘audit trail’ that also records calibration activity, all of which may be extracted using PC software.

Calibration:
Two-point calibration in any selected scale allows accurate control of measurement. Typically ZERO or low-point calibration is made with water. However, unlike other manufacturers’ instruments where only water may be used, all Bellingham + Stanley laboratory refractometers allow zero calibration with liquids other than water (1.33299 RI). This feature is particularly important for calibrating a narrow range high up the refractive index scale or for calibration at elevated temperatures, where water becomes unstable near its boiling point. Additionally, legislation within the pharmaceutical industry dictates use of Certified Reference Material’s as part of a validation, in which case a low value AG fluid that has superior traceability than water may be a more suitable option for setting the zero point.

SPAN, or top-end calibration, facilitates control at the upper end of the scale at any selected point above ZERO but ideally at the upper limit of the measurement scale of the samples under test.

Please note that Bellingham + Stanley refractometers do not require three or multi-point calibration. Verification at a mid-point should in all cases show the instrument to be performing within its measuring specification. No further calibration is therefore necessary. In the unlikely event that after calibration, the refractometer is not performing within specified tolerances and after repeating the procedure, contact Bellingham + Stanley or an approved service centre. Also worthy of note is that for optimum performance, calibration points should be at opposite extremes of the measurement range with the lowest value used to set zero and the highest to set span.

Automation:
RFM900 series refractometers provide both mechanical and electrical connection to other instruments and automated systems. A micro flowcell provides the connection for pumped sample from an autosampler in beverage and fragrance & flavours systems, whilst funnel flowcells give rapid readings in busy sugar laboratories. Full details of automated systems are available on request.

Certified Reference Materials:
Bellingham + Stanley supply a wide range of UKAS certified calibration materials manufactured in accordance with EN ISO/IEC 17025:2005 and traceable to International Standards² suitable for use in the verification procedure of any make or model of refractometer or polarimeter at 20 °C.

Additionally, software on this website allows refractive index values of CRM’s at other temperatures to be instantly displayed allowing rapid calibration at elevated temperatures³.

PC Software:
As discussed throughout this section of the website, RFM900 series refractometers are supported by a range of PC software programs that allow the user to perform a number of external functions. Creation of user scales and temperature co-efficient is made easy, whilst extracting audit trails is an important procedure for pharmaceutical industries under FDA regulation. All PC software is available free of charge from this site as a value-added item offering a measurement solution without any high cost hidden extras!

Technical Notes:

1. English, French, German, Spanish available as standard.  Selected other languages are available on request at time of order only and in association with certain distribution outlets.
2. International Commission for Uniform Methods of Sugar Analysis (ICUMSA), National Institute of Standards Technology, USA (NIST) and/or Physikalisch-Technische Bundesanstalt, Germany (PTB)
3. Temperatures other than 20 °C are not covered by the accreditation scope of UKAS Certificate 0834.