UDT Instruments Model 431 X-Y Optical Position Indicator
When interfaced with tetra-lateral devices, pin-cushion photodiodes, or quadrant detectors, the Model 431 determines the X and Y location of the centroid of a light spot on the detector (the Model 431 is incompatible with duo-lateral detectors).
The Model 431 uses a network of analog amplifiers and dividers. The first amplifier stages operate in the transimpedance mode, boosting the photodetector current and converting it to a voltage. The secondary stages add and subtract the signals from each of the front-end amplifiers. A divider network divides the difference by the sum. And a final buffer amplifier drives the digital display and analog output.
The front-end amplifier gain adjusts over 4-1/3 decades. This lets you optimize the signal-to-noise ratio for the incident light level. The sum and difference stage gain adjustments establish the detector’s sensitivity light spot movement. With the front-panel quadrant/continuous select switch, you select the appropriate amplifier sequence as a function of the detector type in use.
Five BNC connectors on the rear panel present the X position, Y position, X sum,Y sum, and total sum signals. The position signals are scaled from 0 to ±2VDC (to coincide with the 3½ digit display), and sum signals range from 0 to +10VDC. A printed circuit board edge connector also provides each of the four preamplifier outputs, the X and Y difference outputs, and test voltages from the power supply (+7V, -7V, +15V, -15V).
- UDT Instruments Model 431 Optical Position Sensor Data Sheet
- UDT Instruments Model 431 Optical Position Sensor Manual
UDT Instruments Model 531 X-Y Optical Position Indicator
When interfaced with continuous or segmented position sensing detectors, the Model 531 determines the location of the centroid of an incident light spot, and displays its X-Y position both digitally and graphically. This position information may then be transferred by computer over a built-in IEEE-488 interface.
The Model 531 contains an analog preamplification section, and a digital processing and I/O section. The analog front end is isolated from the digital section by an electrically shielded enclosure within the 531’s housing. This shielded section can house two analog cards which plug into the back panel. The analog amplifier stage operates in the transimpedance mode to boost the photodetector current and convert it to a voltage. The digital section is essentially a microcomputer based on popular bus architecture. It controls an A/D converter which digitizes the voltages from the analog section, and then performs the calculations shown, displaying the results on the dot matrix display. The microcomputer also adjusts the analog gain, controls modulated operation of light sources, and controls the IEEE-488 functions.
For stand-alone operation, the Model 531 is programmed through a tactile touch panel beside the display. The touch keys prompt you through several programming menus for simple setup. The menus let you select the type of detector in use, calibration and scaling factors, and pulsed or DC operation. You can also program the Model 531 via the IEEE-488 interface and remotely control your measurement.
UDTi provides optional LabWindows® compatible drivers for easy interfacing with Windows PCs.
The unit provides a 100 mA current source to drive an LED in either DC or pulsed mode. Optionally, a second analog card can be plugged in to permit the operation of a second dual axis position sensor (or 2 more single axis devices). Two sensors provide “depth” perception for 3-D position sensing.
The Model 531 is compatible with all position sensors including duo-lateral, transparent duo-lateral, single and dual axis tetra-lateral, pin-cushion types, and bi-cell and quadrant detectors. The instrument comes in a 19″ rack-mountable case. An instruction manual and power cord are provided.