P445/000/000 - Integration Controller Module
The Integration controller module has been designed as a supplement to systems which are designed for continuous signal measurements. Such systems do not support the integration sampling mode on the PMT amplifier as the appropriate timing and control signals are supplied by the wavelength changer electronics. To extend the operation of these continuous measurement systems, the integration controller has been designed to provide variable integration control from 0.1ms to 100s. It can be plugged into any empty bay on a standard Cairn photometry rack, and will provide the appropriate signals for all PMT amplifiers present.
What is the purpose of the integration mode?
One of the reasons our photometry modules have given such good results over the years is that they normally work by integrating the optical signals over an appropriate period of time. This form of operation is particularly useful in dual or multiple excitation systems, since the integration period can be matched to the time during which a particular excitation wavelength is present, and the integrated output is a direct measure of the total amount of light detected during the integration period.
For systems where no wavelength changing is required, such as when measuring a continuous optical signal, a simpler configuration is often used where the output signal is filtered to some degree to reduce noise. The problem with this type of arrangement is that the filtering needs to be matched to the sampling rate of the subsequent data capture system. Insufficient filtering for a given sampling rate means that the data will be more affected by high-frequency noise, whereas too much filtering means that the response time will be increased, so that genuine signal changes will be smeared out over a number of successive data samples. By using an integration method, and matching the integration time to the sampling rate, this problem is removed. For a given light level, the output depends on the integration time, but in practice this is a very useful additional way of controlling the gain of the system.
