The 3B45 and 3B46 are single-channel isolated frequency input modules which produce simultaneous precision voltage and current outputs proportional to input frequency. Model 3B45 accepts full-scale inputs ranging from 25 Hz to 1100 Hz, while Model 3B46 accepts full-scale inputs from 520 Hz to 25 kHz. Both models enable the user to set the threshold to either 0 V (for zero crossing signals) or +1.6 V (for positive level signals), and the hysteresis to either 0 or ± 4 V. Hysteresis can be set for any value within this range using the optional AC1310 ranging card. The 3B45 and 3B46 shield their computer side outputs from damage and loss of signal integrity from field-side overvoltage faults, withstanding up to 220 V rms at their input terminals. The current output withstands 130 V rms without damage and interfaces user equipment through screw terminal connections. In addition, all 3B45 and 3B46 models are plug-in, mix-and-match and hot-swappable, so each can be inserted or removed from any socket in the same backplane without disrupting system power.
3B Series Custom-Ranging Program
Externally-programmable Models 3B45-00 and 3B46-00 enable the user to configure a special input range by using the optional plug-on AC1310 ranging card, which houses user-supplied resistors to determine hysteresis, zero and span. To facilitate selecting resistors, a Windows® program, 3B-CUSTOM, calculates resistor values based on the user-desired input/output ranges.
Inside the 3B45 and 3B46 Series Module
The 3B45 and 3B46 compare the input signal to the user-selected threshold (Vt) and hysteresis (Vh). Signals of virtually any wave shape that exceed the combined threshold and hysteresis levels (Vt ± Vh) will trigger a comparator at a rate determined by the input frequency. The comparator output is then transmitted across a proprietary transformer-coupled isolation barrier. A demodulator on the computer side of the signal transformer recovers the original signal, which is then filtered and buffered to provide a low-noise, low-impedance output voltage; this output also drives a voltage-to-current (V/I) converter to provide a simultaneous current output for interfacing versatility.
Simple Setup and Versatile Choices
Setting the threshold value is a simple matter of externally wiring to the 3B Series backplane screw terminals. The threshold for measuring a zero-crossing voltage waveform (such as sine waves) can be set to 0 volts by connecting terminal 3 connected to terminal 4. The threshold for a positive level signal (such as a TTL or pulse train waveform) can be set at +1.6 V by connecting terminals 1 and 2. Hysteresis for both input signal types is set at 0 V, but can be changed to ±4 V by removing the jumper that is installed on the AC1310 ranging card.