Ithaco Dynatrac 3 Lock-in Amplifier 393-02 Ratio Option 02 Synchronous Detection

Ithaco Dynatrac 3 Lock-in Amplifier 393-02 Ratio Option 02 Synchronous Detection

The Ithaco Dynatrac 3 is an analog lock-in amplifier (model 393-02) designed for synchronous, phase-sensitive detection of weak signals buried in noise. This unit is equipped with the Ratio Option 02 module, which adds ratiometric measurement capability for normalized output readings. It is being sold AS-IS for parts or repair and has not been tested at our facility.

Specifications & What's Included

• Manufacturer: Ithaco
• Model: Dynatrac 3, 393-02
• Option installed: Ratio Option 02
• Form factor: Rackmount, 2U chassis with rack ears
• Output meter: Dual-scale analog meter — A cos Ø (±10 range) and A sin Ø (±3 range)
• Time Constant: ~100 ms to 4.0 s (front panel rotary selector)
• Zero Suppress: front panel rotary control (0–8 range)
• Signal Mode: Normal, 1000%, 100%, Max Output Stab, Max Noise, Hi Ω, Lo Ω, x1, x10, x100 (front panel toggle/selector)
• Sensitivity: 3 mV to 100 mV visible range on front panel dial (20 dB scale)
• Input: BNC — selectable Isolate / Ground (front panel switch)
• Outputs (front panel): A cos Ø, A, A sin Ø via BNC connectors
• Reference section: Range 10 Hz–100 Hz and 100 Hz–1 kHz; Mode — Sig Track, INT, EXT, EXT 2I
• Frequency dial: rotary, 1–4 scale with Ref Unlock indicator LED
• Phase control: 0–180 degrees rotary dial; 0°, 90°, 180° output connectors (rear)
• Ref In / OSC Out / OSC Level connectors on front panel
• Ratio Option 02 rear module: Y Level knob with Lock, Meter selector (Y In, X, Y, X÷Y, Out), BNC I/O, ÷ = 1.00 / ≈ 1V Full Scale
• Output Rolloff: 6 dB/oct or 12 dB/oct (rear panel switch)
• Rear outputs: A cos Ø, A, A sin Ø (BNC)
• Preamp connector: 5-pin DIN (rear panel)
• Power: 90–130 VAC MDL 3/4A-SB fuse; 195–260 VAC MDL 3/8A-SB fuse (selectable)
• Interior: multiple PCBs visible with through-hole components, transformers, and capacitors — appears complete
• Included: unit only — no manual, cables, or accessories

Applications

Lock-in amplifiers like the Ithaco Dynatrac 3 are used in scientific and research settings to recover small AC signals that would otherwise be undetectable against background noise. The technique relies on phase-sensitive detection: the instrument multiplies the input signal by a reference frequency and filters the result, effectively narrowing the measurement bandwidth to a very small window around the reference. This makes it possible to measure signals orders of magnitude smaller than the noise floor. The Dynatrac 3 was used in university and government research labs during the 1970s and 1980s for applications including optical spectroscopy, photoacoustic measurements, modulated light-source experiments, magnetic resonance, and low-level sensor signal recovery. The Ratio Option 02 adds ratiometric normalization, which is useful when the signal must be divided by a simultaneously measured reference quantity — common in transmission or reflectance spectroscopy setups. Ithaco (based in Ithaca, NY) was a well-regarded manufacturer of low-noise amplifiers and lock-in instruments during this era, and their instruments remain sought after by researchers maintaining legacy setups and by those building custom analog measurement systems.