Interrogation unit

Individual or multi-probe transmitter units are available that are mounted local to the probe and used to receive, process, and transmit the probe signals to a remote interrogation unit. The interrogation unit may be either a dedicated chart recorder, a digital display unit or a process computer. 

It would normally be necessary to locate more than one monitoring unit on a structure. Thus each unit will only transmit its information on receiving coded instructions. Surface units can commonly accommodate up to 80 different codes. The ability to interrogate and receive over any distance is dependent upon the acoustic operation frequency. Relatively high frequencies are preferable, as they avoid problems of pulse reverberations and echoes from structural members. Typically data can be transferred over a distance of 2 km. This type of acoustic unit gives accuracies in potential measurement of 10mV. 

Freeze-drying is another unit operation that has been interrogated with in situ NIR spectroscopy. A group in AstraZeneca R D has demonstrated how the process insight provided by NIR was complementary to and corroborated by the information obtained from temperature monitoring.60 Their work was demonstrated in a pilot-scale facility and involved the construction of special equipment to ensure a representative sample. 

Thermistors can be connected to a microprocessor-based memory element and packaged as a portable element. When the temperature-memory-pack unit is retracted from the process, it can be interrogated by a computer to store the... 

The CpCo platform has been employed to display and interrogate the dithiolene unit with respect to the ligand-based reactivity. The dithiolene ligand cannot, however, be readily removed from the CpCo site. 

For TRXRD measurements to be meaningful, special attention must be devoted to the questions posed, to the manner in which the experiments designed to answer these questions are performed, and to the proper choice of materials and complete documentation of experimental protocols and results. As an example, in the case of a T-jump experiment, documentation should include direction, rate and magnitude of the jump, initial and final temperatures, and the thermal history of the sample. Ideally, in-sample temperature should be recorded at or close to the interrogating X-ray beam throughout the course of the transition. The manner in which the characteristic transition time is determined must be adequately described and, where possible, an estimate made of the number of molecules transforming per unit of time and volume. A measure of the sensitivity of the detection system to the presence of intermediates or minor and disordered phases would enormously benefit data evaluation. 

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