The Model 3000 Control/Data Acquisition Unit (M3000) is a flight-quality controller for control and data gathering functions associated with quartz crystal microbalances. The Model 3000 was designed to meet the growing need for a cost-effective, yet efficient means of interfacing various QCM mass sensors (MK10, MK16, MK17, MK18, MK19, MK20, MK21, MK24, and MK26) for flight operations.

The M3000 communicates over an industry standard RS-232 or RS-422 serial link. It accommodates both Si-diode and PRT temperature sensors, and will drive wire wound heaters, PRT heaters, and single, dual and 3-stage thermoelectric elements. Additionally, it is able to power an external heater, such as is used for an effusion cell.

While autonomously controlling the temperature, both temperature and frequency data for each channel are sent over the serial link and as output analog voltages (0 to 4.096V). The temperature settings and data have a range of -128°C to +128°C and a resolution of 0.0625°C. The frequency sampling rate can be user customized to meet the application’s needs providing programmable sampling period of 25msec. to 1.275sec ±5msec and summing of 2 to 4095 sample periods or 50msec to 1:27:02.125 hours. Frequency data sent in hertz and is counted up to 65,535 during each sample period. Modular in design, it can be stacked to power 2 to 8 QCMs. It can be designed to run on regulated or unregulated power.

System housekeeping is provided for a variety of parameters including CPU temperature, 5V power supply, TQCM amplitude, duty cycle, and PRT current. An analog health bit is provided as are three servo controls to customize system operation.

The system is capable of driving QCM cable lengths of up to 75 ft. (23 m).

The Model 2000 Control/Data Acquisition Unit (M2000) was designed to meet the growing need for a cost-effective, yet efficient means of interfacing any combination of up to twelve of our various QCM mass sensors to a general purpose host.

With a minimal front panel, the M2000 communicates with the host computer over an industry standard RS-232 serial link. It accommodates both Si-diode and PRT temperature sensors, and will drive wire wound heaters, and both single and dual thermoelectric elements. Additionally, it is able to power and external heater, such as is used for an effusion cell.

While autonomously controlling the temperature, both temperature and frequency data for each channel are sent to the host over the serial link. The base unit can handle four channels, expandable to twelve channels in steps of four. The data is sent to the host at a rate of one reading per second per channel.

The temperature data sent to the host is given in degrees Kelvin, with the least significant digit representing 1/100 of a Kelvin (0.01ºK). The electronics add no more than ¼ of a Kelvin (<0.25ºK) error to the accuracy of the sensor for absolute accuracy. For relative accuracy, which eliminates thermal drift, the added error is less than 1/10 of a Kelvin (<0.1ºK). Frequency data sent to the host is given in Hertz. The relative accuracy is better than one part per million (>1 ppm). For all frequencies (1 KHz to 600 KHz), seven digits with a floating decimal point is sent. Thus, for a frequency of 100 KHz, the least significant digit represents 1/10 Hz (0.1 Hz).

The software included is simple to install and use, with an integral programming language which allows for simple command sequences. If desired, a host computer with software installed can be supplied, or an in-house computer may be used.