Square Wave Pulser/Receiver

The combination of Ritec's SP-801A high power square wave pulser with the BR-640A broadband receiver constitutes the ideal instrumentation for driving EMAT measurements and other ultrasonic testing of high damping materials at low frequency.

 

SP-801A Square Wave Pulser

The SP-801A produces negative high power square pulses with fast rise and fall times with extremely low output impedance (~4 Ω). The negative 400 V rectangular pulse is adjustable in 2 dB steps down to -50 V (-20 dB setting). This provides a simple, reproducible way of controlling the signal amplitude. Step-up transformers are optionally available for use with high impedance piezoelectric transducers or low-frequency EMATs to produce drive levels up to 1200 V. Additionally, specific matching networks for use with EMATs are also available.

Very high pulse power output

The low output impedance of approximately 4 Ω makes possible pulse powers of approximately 10 kW when working into a matched 4 Ω load. The average power output is limited to 4.5 W by circuitry which automatically shuts down the high voltage supply.

Pulse Width optimized for transducer frequency

The pulse width control for the SP-801A has eight positions, four of which are set for operating frequencies of 0.5, 1, 2.25 and 5 MHz. The remaining four positions allow continuous width control from less than 25 ns to greater than 14 µs. This makes it possible to adjust the width for half the period of any operating frequency from 50 kHz to greater than 20 MHz. Wider or narrower pulse widths (lower or higher frequency) available on special order; please contact us.

Internal or External Triggering

The internal repetition rate generator may be set from 0.17 Hz to 10 kHz in a 0.17, 0.25, 0.5, 1 ratio sequence through a 20 position rotary switch, or the unit may be triggered externally with either a positive or negative going TTL waveform. In some cases it may be convenient to trigger the unit from an existing spike pulser with spikes of up to 1 W of average power.

 


 

BR-640A Broadband Receiver

The BR-640A is a modestly high gain broadband RF receiver specifically designed for use in ultrasonic systems. It has fast recovery while still being protected against severe overload, allowing its use in a pulse/echo (single transducer) type of operation.

Frequency Range of 100 kHz to 50 MHz

The BR-640A maintains excellent recovery characteristics over its full frequency range. However, when working in the mid to high frequency range, some improvement in recovery time can be achieved by invoking one of the high pass filters. Cut-off frequencies of 100 kHz, 500 kHz, or 1 MHz may be selected. Typically, when single transducer (pulse/echo) operation is employed, high voltages are applied to the receiver input during the driving pulse. The BR-640A input is protected against high voltages and an average power input up to 2 W. When used with a RITEC diplexer the voltage and power to the receiver input will be radically reduced without reduction in signal. The diplexer removes the duty cycle limitations imposed by the 2 W resistor.

Large Gain Control Range

The gain of the unit may be set from -15 to +64 dB in 1 dB steps without sacrificing the 6 dB noise figure except in the very low gain settings. This method of control allows the gain to be set accurately and reproducibly with imperceptible drift.

High or Low Input Impedance

The unit features either a 50 W or high-impedance input (switch selectable) and a 50 W output with a 1 Volt peak to peak swing capability. Auxiliary power is also available for external modules such as pre-amps. Optional matching networks for driving EMATs are available.