DM501

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The Tektronix DM501 is a 4½ digit multimeter plug-in for the TM500 system.

(See DM501A for the significantly different successor model.)

It also has a temperature input, requiring the P6058 or P6430 temperature probe with a 4-pin LEMO S-series connector.

The DM501 MOD718D variant replaced the temperature range with a 200 mV input range providing 10 μV resolution (see Physical Measurements Handbook).

Key Specifications

DC Voltage ranges and accuracy	2 VDC to 200 VDC in decade ranges (0.1% + 0.01% FS), 1000 VDC (0.1% + 0.02% FS)
DC Voltage characteristics	Input resistance 10 MΩ, CMRR >100 dB at DC, 80 dB at 60 Hz (1 kΩ unbal.), NMRR ≥30 dB at 60 Hz + 20 dB/decade
AC Voltage ranges and accuracy	2 VDC to 200 VAC in decade ranges, and 500 VAC (0.7% + 0.01% FS for sine inputs only)
AC Voltage characteristics	Input impedance 10 MΩ // ≤70 pF, CMRR unspecified
DC Current ranges and accuracy	2 mA to 2 A in decade ranges, 0.2% + 0.05% FS
AC Current ranges and accuracy	2 mA to 2 A in decade ranges, 0.6% + 0.05% FS (for 40 Hz to 1 kHz sine)
Ohms ranges and accuracy	2 kΩ to 20 MΩ in decade ranges, current 1 mA to 0.1 μA respectively; 0.3% (20 MΩ: 0.5%) + 0.01% FS
Temperature range and accuracy	–55°C to +125°C (±1.5°C), +125°C to 150°C (±2.5°C)

Internals

The DM501 is precise to 4½ digits, but not accurate to 4½ digits. The combination of a D-to-A converter built from opamps and discretes combined with a noisy high-frequency isolated power supply make for barely achievable 3½ digit accuracy over all ranges. Every TM500 DVM after the 501 (including the DM501A, the DM502, and so on) used integrated A-to-D converters and a mains-frequency isolated power supply.

Pictures

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  DM501

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  DM501 open left side

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  DM501 integrator board

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  DM501 integrator board solder side

See also

• Siliconix LD120 and LD121A datasheets
• Fairchild 3814 counter IC
• 307-1015-00 input voltage divider