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Buffer Amplifier and Calibrator Accessory

The Buffer Amplifier is not required for using Mac the Scope.

The Buffer Amplifier and Calibrator Accessory is provided only for users needing to monitor high impedance signals (for instance, tracing signals on circuit boards). The Calibrator output signal is provided as a convenient calibration source.

Features:

• Switchable Input Gain (x1, x10).
• Switchable, 1 kHz (nominal), Square Wave Calibrator Signal Source.
• Can be used with Mac the Scope's AUTO CAL feature.
• Battery powered (lithium coin - type primary cell), micropower CMOS circuitry.

Inputs:

• Two, BNC type connector.
• Impedance 10 megohms, single-ended, capacitor coupled (metallized polypropylene).
• Protected up to 40 volts AC or DC.

Outputs:

• Two, RCA (phono) jack, single-ended (also connects to optional Mac the Scope interface cable).
• Effective output impedance: 10 ohms.
• Rated output load: 1000 ohms or greater.
• Noise (referred to input, inputs short circuited, Gain = 10): 70 microvolts peak to peak, 1 Hz to 20 kHz.
• Maximum output swing: 6 volts peak to peak.

Nominal Frequency Response (- 3 dB cutoff points):

• 0.1 Hz - 20 kHz (Gain = 1).
• 0.1 Hz - 10 kHz (Gain = 10).

This frequency response is adequate for use with a 44.1 kHz sample rate, and is limited by the LMC6042AIN micropower operational amplifier, whose design trades speed for low-power operation.

Semiconductors:

• Buffer: National Semiconductor LMC6042AIN micropower CMOS operational amplifier.
• Oscillator: CD4011.
• Voltage Reference: Zetex ZRA12501.
• The buffer and oscillator chips are socketed.

Battery Life:

• Over 3 years at rated current (Calibrator Signal Source off).
• Battery Current: 20 microamperes nominal, inputs open; 500 microamperes, Calibrator Signal Source activated.
• Battery Type: Two, Panasonic CR2354, 0.56 ampere - hour; other 0.91" diameter lithium coin cells may be substituted.

Enclosure:

• Flame Retardant ABS, 6.52" x 2.78" x 1.14"

Circuit Board:

• UL94VO glass epoxy.

Calibrator Signal Source:

• Frequency: 1 kHz + / - 10%, bipolar waveform.
• Output Amplitude: 600 mV peak to peak nominal (Gain = 1), regulated.
• Each unit tested with NIST (NBS) traceable reference; actual calibrator output amplitude value is provided with each unit.

The Calibrator output is intended for computers with line-level inputs. PowerPC and the Quadra AV series computers have line level inputs. Computers with "Microphone Level" inputs are designed for smaller input signal levels, and will be unable to use the Calibrator feature.

Calibrator Output Waveform

The output frequency of this calibrator unit was 926 Hz, with a measured amplitude (plateau to plateau) of 0.614 V (either channel). Mac the Scope's AUTO CAL feature is relatively insensitive to asymmetry and waveform frequency, because automatic calibration is performed plateau - to plateau on the square wave.

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