The Tektronix DM504A is an 4½ digit autoranging digital multimeter plug-in for the TM500 system.

Tektronix DM504A
4½ digit autoranging digital multimeter
Tektronix DM504A

Produced from 1989 to (?)

ROM Images
File Pos. Checksum
(All manuals in PDF format unless noted otherwise)

Key Specifications

DC Voltage 200 mV to 1000 V in decade steps, ±0.05%; Input resistance 10 MΩ (200 kΩ in 0.2 and 2 V ranges if Vin > 12 V)
AC Voltage 200 mV to 500 V in decade steps, ±0.6%; Input resistance 10 MΩ // 100 pF
DC current 200 μA to 2 A in decade steps, ±0.1%;
AC current 200 μA to 2 A in decade steps, ±0.6%;
Resistance 200 Ω to 20  MΩ in decade steps, 0.05% (0.1% in 2 and 20 MΩ ranges
Temperature −62 °C to +230°C with P6602 2-wire PT-100 probe
Display 4½ digits, red LED, 2/s update rate
  • Modes: DC Volts / mA, AC Volts/ mA (True RMS), Ohms, and Temperature
  • Diode Test and Audible Continuity (Beeper) Modes


Documents Referencing DM504A


The DM504A has no rear interface I/O. The entire circuit is supplied from a +12/−12/+5 V floating power supply that uses a small mains-frequency transformer fed by one of the mainframe's 25 VAC windings.

The circuit is based on an 80C31 microcontroller with a Texas Instruments TL500C integrating A/D front-end and a 1N827 temperature-compensated zener reference. The DM504A is software-calibrated, storing cal constants in a 93C46 EEPROM. Calibration is triggered by pressing Up and Down buttons simultaneously while the internal cal jumper is in the "enabled" position.



Some Parts Used in the DM504A

Part Part Number(s) Class Description Used in
AD737 156-3506-00 Monolithic integrated circuit RMS/DC converter DM504A
Intel 8031 Monolithic integrated circuit 8-bit microcontroller 571 DM504A