The TMc300 range of monochromators control grating position using precision gears and a microprocessor-controlled microstepping drive. Up to three gratings are mounted on a turret which can be rotated through 360° allowing software selection of grating type and position.
A programmable detector changeover mirror and detection electronics with software selectable dual inputs allow spectral scans over wide wavelength ranges to be accomplished without manual intervention. The advantages of this drive include constant wavelength accuracy at all grating angles, very fast wavelength acquisition and zero backlash.
The optical layout of these instruments has been developed to minimise scattered light and maximise throughput. Effective internal baffling reduces general scatter while the novel mirror arrangement avoids rediffracted light which is often a problem shorter wavelengths. The use of large rectangular gratings enhances light throughput and maintains constant f number at high grating angles. As an option, for use with array detectors, the focusing mirror can be mounted on an externally controllable translation stage which allows fine focusing without disturbing the array. As with all Bentham monochromators, the TMc300 is built in a single casting, giving the best rigidity and robustness.

Configuration: Czerny-Turner
Slits: 10µm to 10mm variable, fixed or motorised
Slit height: 20mm
Number of gratings: 1,2 or 3
Grating size: 68 x 84mm
Aperture ratio: f/4.1 (at all grating angles)
Resolution: 0.1nm at reduced slit height, 0.3nm with full slit height of 20mm, both measured with 1200g/mm grating
Dispersion: 2.7nm/mm (1200g/mm)
Mechanical resolution of grating drive: 0.00072 degrees per motor step
Wavelength acquisition speed: 1000nm/sec
Wavelength accuracy: +/- 0.2nm over full range of 1200g/mm grating
Wavelength repeatability: +/-0.05nm (1200g/mm)

For those applications where the scattered light performance of a single monochromator is not sufficient, the DTMc300 double monochromators are available. These devices are supplied with either additive or subtractive dispersion, or they can be converted from one to the other by changing one of the grating turrets and the controlling software. A swing away mirror allows instant change from double to single operation - a useful feature in UV-VIS-NIR systems. An order sorting filter wheel, essential for accurate measurement of continuous spectra, motorised slits, light sources and detectors are amongst the wide range of light measurement products available to complement the TMc300 family.