instructions.htm

	DESIGNED & OPTIMISED EXCLUSIVELY FOR MODERN F-T INFRARED & NIR SPECTROMETERS

NIR TRANSMISSION
SPECTROSCOPY
PRECISION HEATED CELLS
- SERIES HNIR

OPERATING INSTRUCTIONS

THE SYSTEM

The Ventacon system comprises of a cell to fit any near infrared spectrometer with 2"x3" industry standard sample holding rails in the sample chamber. The cell has a rectangular sample holding zone and will accept cuvettes up to 20mm in path length. To hold the cuvettes and to maximise the transfer of heat two metal spacers are provided. The cell is closed with a precisely fitted lid. The cell oven is drilled with passageways through which compressed air or water can be passed.

Temperature control is made using low voltage heaters and platinum resistance thermometry. The single output cable will plug into a Ventacon D-2 Universal Power Supply. Monitoring and power control connections are made through the cable. No separate thermocouple is required in this system.

OPERATION

The cell is supplied with its Power Supply and the latter has been configured for the cell. However, we advise that you proceed as follows:

Fit the cell into the instrument and connect its cable to the power supply using the HOT socket. Fit the cuvette and the longest spacer that will go into the cell.
Check the voltage setting for the power supply and adjust is appropriate.
Turn on the supply. After a few seconds the temperature controller will read the temperature of the cell. Switch the power supply to HOT.
Press the left hand button on the CAL controller and you will see the 'set' temperature. Adjust using the and buttons to your requirements.
The temperature will now rise. You can use high power to hurry the process but you must lower the energy as you approach the set temperature.
Leave the cell for 5 minutes to allow the temperature of the sample to rise. Remember, the cuvettes are made of silica, a material with poor thermal conductivity. Set the power to MEDIUM above 50º or LOW for set temperatures below this.
Activate the Autotune routine. (See instructions below).
The temperature should set very accurately after tuning.

If you change the set temperature by more than 10º OR change the sample size (path length or depth) you should autotune again to maintain best performance.

COOLING THE CELL

It is possible to pass water through the cell using the two connections on the end. We prefer that you use compressed air for cooling. There is little point in cooling very rapidly, as the sample will not follow the temperature of the cell. It is permissible, of course, to pass thermostatted water. If the power supply is tuned on, the controller will read the cell temperature but the output knob must be switched to COLD or the power supply will try to heat the cell. In a sense passing thermostatted water is not to be recommended because the cell itself can be controlled more precisely than the water.

PRECAUTIONARY NOTE

After the use of water the internal passages in the cell MUST be blown out with compressed air. If drops of water are left inside the cell, the temperature control will be poor especially above 100º set.

DISMANTLING

The cell is not designed to be dismantled routinely. The two windows can, however, be replaced. The front window is accessed by removing the small screws in the 3"x2" plate. DO NOT OVER TIGHTEN THEM. Removing the rear window is much more difficult. Please request help before attempting removal.

CLEANING

The windows are best cleaned using petroleum ether on a cotton wool bud.

[Heated NIR Cell]