The Keithley CTM-05A is an ISA-bus counter/timer board for PC-based test systems, delivering precise timing and event measurements across five independent 16-bit counters. Built around the industry-standard 9513 counter/timer chip, it supports frequency, period, pulse width, and event counting up to 7 MHz input rates. The board enables software linking of all five counters to construct 32-, 48-, 64-, or 80-bit counting chains, making it suitable for automated testing, data acquisition, and process control requiring high-resolution timing accuracy.
## Technical Specifications
**Counter Architecture**
• Five independent 16-bit counters with up/down counting in binary or BCD format
• Maximum input rate: 7 MHz
• Load and Hold Registers on each counter
• Frequency measurement to 7.5 MHz (requires two adjacent counters)
• Pulse width measurement: 70 ns minimum (high and low)
• Period measurement supported
**Pulse Output Capabilities**
• Available on channels 0–4
• Minimum pulse width: 2 µs
• Minimum pulse period: 4 µs
• Maximum pulse period: 2,147 seconds
**Event Counting**
• 16-bit mode (channels 0–4): maximum 65,535 counts
• 32-bit mode (channels 0–3): maximum 4,294,901,760 counts
**Onboard Time Base**
• Selectable 1 MHz or 5 MHz
• Accuracy: ±0.01% over 0–70°C
**Digital I/O**
• 8-bit input and 8-bit output ports
• Counter inputs software-selectable for active-high or active-low
• Hardware or software gating per counter
• 40-pin header for digital I/O connector
**Electrical Characteristics**
• Input low: 0.8 V max, 1 mA max current
• Input high: 2.2 V min, –10 µA max current
• Output low: 0.4 V max at 3.2 mA
• Output high: 2.4 V min at –200 µA
## Key Features
• Software-linked counter chains up to 80 bits
• Dual-mode counting (binary or BCD)
• TTL-compatible I/O levels
• Hardware and software gating control
## Compatibility & Integration
Standard 37-pin D-type male connector with mating 37-pin D-female (ITT/Canon DC37S equivalent). Optional accessories include CA4037 cable, STC-37 screw terminal connector, STA-U Screw Terminal Board, and STP-37 Screw Terminal Panel (with C1800 cable).
