Although our photometric systems are usually used with microscopes they can also be configured as a standalone instrument based around our cuvette holder.
This assembly accepts a standard 1cm x 1cm cuvette. It consists of an outer and an inner section. The inner section, which surrounds the cuvette, is insulated from the outer housing, and its temperature can be controlled by circulating fluid through its internal perfusion pipes. These are brought out towards the bottom of one face of the assembly.
There are two electrical sockets on the assembly. The socket on the face opposite the perfusion pipes connects to an internal temperature sensor. This can be used to read the temperature in conjunction with a volt meter and an external voltage source. The voltage source (which can be a 9 volt battery) should be connected between the central pin (positive) and the rightmost pin. The volt meter should be connected between the rightmost pin (negative) and the pin immediately to its left (positive) see below.
The other two pins on this connector power a built-in electrical heater. The heater is a power semiconductor, which requires 10-12V in order to pass current (the leftmost pin is positive, and the one immediately to its right is negative). The power supply should have constant-current characteristics, as the voltage across the heater is relatively independent of the drive current. This arrangement has been chosen because it is more efficient than a resistive characteristic when driven over a range of powers from a conventional series-pass regulator (i.e. less energy is dissipated in the regulator circuit). We have intended to design a heater module for some time now, so please let us know if you want a quotation.
The connector adjacent to the perfusion pipes is for the built-in stirrer head. This connects to the stirrer control box with the cable provided. Either of the two sockets on the control box can be used.
The optical arrangements of the cuvette holder are completely symmetrical, with a port on each of the four vertical faces. The port on the surface with the perfusion pipes is nominally designated the input port. The other three are nominally output ports. Of these, the port on the opposite face is intended for optical absorbance measurements, whereas either or both of the two 90° ports are for fluorescence measurements. The cuvette holder is normally supplied with the absorbance port and one of the fluorescence ports blocked off, but the components are interchangeable. Connection to the ports is analogous to that on the photomultiplier connector boxes. Interchangeable filter holders and photomultipliers can be fitted to the three detection ports as required. Excitation light is normally introduced by connecting the cuvette holder directly to the liquid light guide supplied with our optical adapter.
If interchangeable filter holders are not needed all ports have space for accommodating a 12.7mm round optical filter in the light path. The filter sits in a recess in the face of the cuvette holder, and is held in place by the port adapter. Please note that we can supply neutral-density filters of this size, and since they are only 1-2mm thick there may be room for both an interference filter and a neutral-density filter if required.
