DM504A

Tektronix DM504A
4½ digit autoranging digital multimeter Tektronix DM504A Produced from 1989 to (?) Manuals DM504A Operator Manual 070-6945-00 DM504A Service Manual 070-7135-00 ROM Images 160-5426-05 / 160-5426-00 (27C64) please add (All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

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

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
Features	Modes: DC Volts / mA, AC Volts/ mA (True RMS), Ohms, and Temperature Diode Test and Audible Continuity (Beeper) Modes

Links

DM504A @ barrytech.com
DM504A repair by VintageTEK Museum @ YouTube

Documents Referencing DM504A

Internals

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 V_AC 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.