Models AA41-4 Four Channel Frequency Conditioner
is a four-channel conditioners for measuring rpm, flow, and other phenomena that can be sensed by pulse transformer transducers with 2-wire isolated windings (tachometer pickups, turbine flowmeters, etc.), transistor or logic-circuit drivers, “zero-velocity” (true digital output) sensors, and similar frequency- generating transducers. The AA41 accepts a wide range of waveshapes and voltage levels. A “Smart Schmitt” threshold level for each input channel may be individually selected via internal jumper connections, depending on the expected peak voltage input: 0.1-2 V; 0.5-10 V; 2.5-50 V; or 10-200 V. This ensures reliable triggering when the input is at the low end of the voltage range. All ranges are protected against an overload of up to 200 V. Nominal ±5 V-DC excitation is supplied for use with a “zero-velocity” sensor. Standard AA-card “F1” programmable filter tiles let you tailor the dynamic frequency range and signal response of each AA41 channel to your application’s requirements. Setting a frequency channel’s programmable filter to the 1.6-Hz cutoff provides the following input ranges:
- 10% to 100% of full scale for a range of 250 or 500 Hz
- 2% to 100% of full scale for a range of 1 or 2 kHz
- 1% to 100% of full scale for a range of 4, 8, 16, or 32 kHz
If a faster response is more important than dynamic range, you may select a higher “F1” bandwidth value. However, programmable filter settings above 25 Hz are not recommended for use with the AA41, because of inadequate usable dynamic frequency range. When the card is used in System 10, its filter cutoff values are set by means of an on-board 16-position switch for each channel. Capacitive coupling of 0.1 or 10 microfarads is provided for low-frequency inputs, to eliminate false triggering by signal noise and/or any positive or negative DC offset that exists for the frequency signal. A special trigger-level control guarantees reliable triggering when the input is at the low end of the frequency range, while a precise 2.4576-MHz crystal frequency reference ensures accuracy of all calibration, whether “CALCULATED” or “TWO-POINT DEADWEIGHT).” A nominal ±5-V ANALOG OUTPUT is produced by each active AA41 input channel, for purposes of real-time signal monitoring. Each of these “Auxiliary Outputs” is available on a corresponding mainframe wire-wrap pin.