DM501
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 temperature probe with a 4-pin LEMO S-series connector. The manual states that certain NPN transistors such as a 2N2484 may be used as temperature sensors in place of the probe with little or no selection of the transistor.
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 | 2 VDC to 200 VDC in decade ranges (0.1% + 0.01% FS), 1000 VDC (0.1% + 0.02% FS); 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 | 2 VDC to 200 VAC in decade ranges, and 500 VAC (0.7% + 0.01% FS for sine inputs only); Input impedance 10 MΩ // ≤70 pF, CMRR unspecified |
| DC Current | 2 mA to 2 A in decade ranges, 0.2% + 0.05% FS |
| AC Current | 2 mA to 2 A in decade ranges, 0.6% + 0.05% FS (for 40 Hz to 1 kHz sine) |
| Ohms | 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 | –55°C to +125°C (±1.5°C), +125°C to 150°C (±2.5°C) |
Options
- Option 1: Ordering without P6058 Temp Probe
- Option 2: Without Temp Capability and Probe (visible by no Temp Out at the Front)
Links
- Tektronix DM501 Check in and Calibration by Zenwizard Studios @ YouTube
Documents Referencing DM501
Rear interface
The DM501 has a rear input, selectable by a front-panel button, on B28 (Hi) / A29 (Lo), and digit-serial BCD outputs (TTL), see below. The manual does not specify a limit to the input voltage on the rear interface but since this uses card-edge pins adjacent to logic output pins, sticking to the the DM501A specification (200 V peak / 100 V RMS) appears prudent.
Internals
The DM501 is precise to 4½ digits, but not accurate to 4½ digits. The combination of an ADC 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
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DM501 rear interface
Components
Some Parts Used in the DM501
| Part | Part Number(s) | Class | Description | Used in |
|---|---|---|---|---|
| 307-1015-00 | 307-1015-00 | Discrete component | resistor network | DM501 |
| Fairchild 3814 | 156-0306-00 | Monolithic integrated circuit | 4½ digit dual-slope DVM controller | 7A13 • 7L13 • 7L18 • DM501 |