AC Voltmeter VT-121

Kenwood, Trio-Kenwood Inc.; Komagane

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  • Year
  • 1978 ?
  • Category
  • Service- or Lab Equipment
  • Radiomuseum.org ID
  • 372409
    • alternative name: Trio Corp.
    • Brand: Jennen

 Technical Specifications

  • Number of Transistors
  • Semiconductors present.
  • Semiconductors
  • Wave bands
  • - without
  • Power type and voltage
  • Alternating Current supply (AC) / 50-60 Hz, 100; 120; 220; 240 Volt
  • Loudspeaker
  • - - No sound reproduction output.
  • Material
  • Metal case
  • from Radiomuseum.org
  • Model: AC Voltmeter VT-121 - Kenwood, Trio-Kenwood Inc.;
  • Shape
  • Tablemodel, with any shape - general.
  • Dimensions (WHD)
  • 128 x 190 x 230 mm / 5 x 7.5 x 9.1 inch
  • Notes

  • The Trio Model VT-121 is a solid-state electronic AC millivoltmeter designed for laboratory, audio-frequency, and ultrasonic bench testing. Replacing earlier vacuum-tube voltmeter (VTVM) designs, the VT-121 utilizes a solid-state differential amplifier architecture and an IC-regulated power supply to eliminate warm-up drift and minimize power consumption.

    • Measurement Ranges & Scales: Measures AC voltages from 100 uV to 300 V across 12 ranges in 10 dB steps (1 mV, 3 mV, 10 mV, 30 mV, 100 mV, 300 mV, 1 V, 3 V, 10 V, 30 V, 100 V, and 300 V full scale). The taut-band analog meter features dual linear voltage scales (0–10 and 0–3) alongside decibel scales covering -80 to +50 dB (0 dB = 1 V) and -80 to +52 dBm (0 dBm = 1 mW into 600 Ω).
    • Input Impedance & Protection: Maintains a constant input resistance of 10 MΩ (±5%) with less than 45 pF parallel capacitance across all ranges. Maximum durable input is 500 V (DC + AC peak), or 100 V (DC + AC peak) on sensitive ranges up to -10 dB.
    • Logic-Controlled Attenuator & Remote Option: Rather than routing input signals directly through the front-panel rotary switch contacts, the 12-position range selector drives a diode-matrix logic encoder that switches relays and FET attenuators. A rear-panel 16-pin connector allows optional remote range switching for production-line testing.
    • Output Amplifier & Relative Reference: Provides a rear/front monitor output delivering 1 Vrms (±10%) at full scale into 600 Ω (±10%), offering 60 dB of gain on the 1 mV range so the instrument can serve as a wideband preamplifier. A front-panel RELATIVE REF control provides up to 10 dB of uncalibrated variable adjustment to set an arbitrary 0 dB reference point for frequency-response measurements.

    Model Variants:

    • VT-121: Standard version with 1 mV maximum sensitivity and BNC input/output connectors.
    • VT-121F: High-voltage variant with 1.5 mV maximum sensitivity, 12 ranges up to 500 V full scale (770 V max input), +56 dBm maximum scale, and BNC connectors.
    • VT-121S: Variant with 1 mV maximum sensitivity equipped with dual input/output connectors.
  • Net weight (2.2 lb = 1 kg)
  • 2.9 kg / 6 lb 6.2 oz (6.388 lb)
  • Mentioned in
  • - - Manufacturers Literature (Instruction Manual VT-121, VT-121F, Vt-121S, 850-2842-10)
  • Author
  • Model page created by Jörg Kulbe. See "Data change" for further contributors.

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