Hewlett Packard 5315A 108-126V Universal Counter,

The Hewlett Packard 5315A is a universal counter instrument delivering precise frequency, period, time interval, ratio, and totalize measurements across a wide dynamic range. Built around a Multiple Register Counter (MRC) architecture with reciprocal counting techniques, it achieves high-resolution frequency measurements even at lower frequencies. The instrument covers 0.1 Hz to 100 MHz on Channels A and B, expandable to 1.0 GHz with optional Channel C. Dual independent input channels provide full measurement flexibility with independent trigger level, slope, and sensitivity controls, plus switchable AC/DC coupling and a low-pass filter.

## Technical Specifications

**Frequency & Period:**
• Frequency: 0.1 Hz to 100 MHz (1.0 GHz with optional Channel C)
• Pulsed RF signals as narrow as 60 ms supported
• Resolution: 7 digits per second of gate time
• Period range: 10 ns to 10⁵ s; resolution down to 1 ns depending on gate time

**Time Interval:**
• Single-shot: 100 ns to 100,000 s
• Averaging: 10 ps resolution
• Minimum dead time (stop to start): 200 ns
• Operator-selectable delay capability

**Input Characteristics (Channels A & B):**
• DC-coupled: 0 Hz to 100 MHz; AC-coupled: 30 Hz to 100 MHz
• Sensitivity: 10 mV rms sine wave to 10 MHz; 25 mV rms sine wave to 100 MHz; 75 mV peak-to-peak pulse (5 ns minimum width)
• Dynamic range: 0–5 V peak-to-peak (DC to 10 MHz); 75 mV–5 V peak-to-peak (10–100 MHz)
• Signal operating range: +2.5 V DC to −2.5 V DC
• Impedance: 1 MΩ nominal, shunted by <40 pF
• Attenuator: X1 or X20 nominal
• Trigger level: Variable −2.5 V DC to +2.5 V DC
• Slope: Independent ± selection
• Low-pass filter: 100 kHz nominal, 3 dB point, switchable

**Time Base:**
• 10 MHz reference oscillator
• Standard stability: ±5 parts in 10⁶ (0–50°C)
• Aging: <3 parts in 10⁷/month after 30 days continuous operation
• Optional TCXO (Option 001): ±1 part in 10⁶ (0–40°C)
• Line voltage stability: <1 part in 10⁷ (±10% variation)

**Display:**
• 8-digit amber LED with engineering units annunciator

## Key Features

• Ratio measurement (A/B) and totalize modes (manual gating, A gated by B)
• Continuously adjustable sensitivity control to 500 mV rms nominal
• Automatic trigger level set to 0 V nominal in SENSITIVITY mode
• Dual-channel architecture for independent or simultaneous measurements