DM502: Difference between revisions

Latest revision as of 05:21, 18 April 2024

Tektronix DM502
basic 3½ digit digital multimeter Tektronix DM502 Produced from 1975 to 1980 Manuals Tektronix DM502 Manual Tektronix DM502 Modification Summary (All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

The Tektronix DM502 is a basic 3½ digit digital multimeter plug-in for the TM500 system.

It was introduced in 1975 and superseded by the DM502A in 1980.

It has an Int/Ext switch that allows alternate input connections via the rear interface to be selected.

The DM502 is available with an input for temperature measurement with a transistor temperature probe (P6430) using an NPN transistor, e.g. a 2N2484 (any NPN-Transistor with h_FE >150 can be used).

Key Specifications

Voltage ranges	200 mV to 200 V in decade steps; 1 kV (DC) / 500 V (AC) top range
Input impedance DM502A	10 MΩ
Current ranges	200 μA to 2 A in decade steps
Resistance ranges	200 Ω to 20 MΩ in decade steps

An "Option 2" instrument deletes the temperature measurement function,

Links

Tektronix DM502 Multimeter Repair by NFM @ YouTube
Tektronix DM 502A Restoration and Calibration for a Viewer @ Zenwizard Studios YouTube

Documents Referencing DM502

Document	Class	Title	Authors	Year	Links
070-2088-00.pdf	Book	TM500 Series Rear Interface Data Book		1975	AF501 • AM501 • AM502 • DC501 • DC502 • DC503 • DC504 • DC505 • DC505A • DM501 • DM502 • FG501 • FG502 • FG503 • MR501 • PG501 • PG502 • PG505 • PG506 • PG508 • PS501 • PS502 • PS503 • PS503A • PS505 • RG501 • SC501 • SC502 • SG502 • SG503 • TG501
070-2088-01.pdf	Book	TM500 Series Rear Interface Data Book		1976	AF501 • AM501 • AM502 • AM511 • DC501 • DC502 • DC503 • DC504 • DC505 • DC505A • DD501 • DM501 • DM502 • FG501 • FG502 • FG503 • FG504 • LA501 • MR501 • PG501 • PG502 • PG505 • PG506 • PG508 • PS501 • PS502 • PS503 • PS503A • PS505 • RG501 • SC501 • SC502 • SG502 • SG503 • SG504 • SW503 • TG501 • TR501 • TR502

Internals

The DM502 circuit is built around a Siliconix LD110/111 DMM chipset.

The entire unit with exception of the temperature circuit can be elevated up to 1 kV above chassis ground. For this purpose, it is supplied through a mains-frequency isolation transformer with a 50 V primary that is supplied from the two 25 V_AC windings in the mainframe connected in series. This transformer feeds a a discrete +5 V regulator, and an RC4194D regulator for +/–12 V.

The rear interface supports a digit-serial BCD output but the manual cautions that only the Temp Out, Temp GND and HI and LO inputs are factory-wired, the BCD connections must be soldered in by the user if needed – presumably because the digital section is not galvanically separated from the floating input ground. In Temperature mode, the floating ground is connected to the chassis ground (because the temperature circuit uses the mainframe's ±33 V supplies) but the V/A inputs are disconnected.

Pictures

DM502 Opt.2 (no temperature function)
DM502 switch with cover off. The cover removes easily using a Pozidriv screwdriver.
DM502 rear interface – see note above

Components

Some Parts Used in the DM502

Part	Part Number(s)	Class	Description	Used in
CA3046	156-0048-00	Monolithic integrated circuit	transistor array	7104 • 7403N • 7503 • 7B53A • 7D12 • DM502 • FG504 • S-52 • Telequipment D34 • 7603 • 7613 • 7623 • 7633
Siliconix LD110/111A	156-0476-00 • 156-0476-00 • 156-1268-00	Monolithic integrated circuit	3½ digit A/D converter	DM502 • DM502A • DM505

@@ Line 1: / Line 1: @@
-{{TM500 | mfg=Tektronix | type=DM502 | function=basic 3½ digit digital multimeter | class=multimeter | image=Tek dm502 e1.jpg | introduced=1975 | discontinued=1988 |
+{{TM500 | mfg=Tektronix | type=DM502 | function=basic 3½ digit digital multimeter | class=multimeter | image=Tek dm502 front.jpg | introduced=1975 | discontinued=1980|
-manuals=
+designers= |manuals=
-* [http://w140.com/tek_dm502.pdf Tektronix DM502 Manual (PDF)]
+* [[Media:070-1726-00.pdf|Tektronix DM502 Manual]]
-* [http://w140.com/smb/DM502A_SM.pdf Tektronix DM502A Manual (OCR, PDF)]
+* [[Media:Tek DM502 mods.pdf|Tektronix DM502 Modification Summary]]
 }}
+It was [[introduced in 1975]] and superseded by the [[DM502A]] in 1980.
 It has an Int/Ext switch that allows alternate input connections via the rear interface to be selected.
-The DM502 is available with an input for temperature measurement with a transistor temperature probe ([[P6430]])
+The DM502 is available with an input for temperature measurement with a transistor temperature probe ([[P6430]]) using an NPN transistor, e.g. a 2N2484 (any NPN-Transistor with h<sub>FE</sub> >150 can be used).
-using an NPN transistor, e.g. a 2N2484 (any NPN-Transistor with h<sub>FE</sub> >150 can be used).
-The DM502'''A''' model adds an input for a PT-100 temperature probe ([[P6601]]), a True RMS converter,
-and offset circuits to read dB directly in all ranges. An "Option 2" instrument deletes the temperature
-measurement function, P6601 temperature probe, and all internal circuits associated with this function.
-The rear interface of DM502'''A''' is limited compared to the DM502: No current input and no reading output, see gallery below.
-The 2 kΩ measurement range (+HI in DM502A) can be used for diode testing, since a current source of 1 mA is active
-and the reading corresponds to the (forward) voltage drop of the diode in Volts. The voltage can rise to a maximum of 10 V.
-A second voltmeter is needed to measure the voltage if 2 V are exceeded.
 {{BeginSpecs}}
 {{Spec | Voltage ranges | 200 mV to 200 V in decade steps; 1 kV (DC) / 500 V (AC) top range}}
-{{Spec | Input impedance DM502 | 10 MΩ or direct JFET input >2 GΩ  (by internal jumper) }}
 {{Spec | Input impedance DM502A | 10 MΩ}}
 {{Spec | Current ranges | 200 μA to 2 A in decade steps }}
 {{Spec | Resistance ranges | 200 Ω to 20 MΩ in decade steps }}
 {{EndSpecs}}
+An "Option 2" instrument deletes the temperature measurement function,
+==Links==
+* [https://www.youtube.com/watch?v=Tx6DtLooCOs Tektronix DM502 Multimeter Repair] by NFM @ YouTube
+* [https://www.youtube.com/watch?v=AfQkfZfGKkw Tektronix DM 502A Restoration and Calibration for a Viewer] @ Zenwizard Studios YouTube
+{{Documents|Link=DM502}}
+==Internals==
+The DM502 circuit is built around a Siliconix LD110/111 DMM chipset.
+The entire unit with exception of the temperature circuit can be elevated up to 1 kV above chassis ground.
+For this purpose, it is supplied through a mains-frequency isolation transformer with a 50 V primary that is supplied from the two 25 V<sub>AC</sub> windings in the mainframe connected in series.
+This transformer feeds a a discrete +5 V regulator, and an RC4194D regulator for +/–12 V.
+The rear interface supports a digit-serial BCD output but the manual cautions that ''only the Temp Out, Temp GND and HI and LO inputs are factory-wired'', the BCD connections must be soldered in by the user if needed – presumably because the digital section is not galvanically separated from the floating input ground. In Temperature mode, the floating ground is connected to the chassis ground (because the temperature circuit uses the mainframe's ±33 V supplies) but the V/A inputs are disconnected.
 ==Pictures==
-===DM502===
 <gallery>
-Tek dm502 e1.jpg
 Tek dm502 front.jpg
+Tek dm502 e1.jpg      | DM502 Opt.2 (no temperature function)
 Tek dm502 left.jpg
+DM502_switch_inside.jpg|DM502 switch with cover off.  The cover removes easily using a Pozidriv screwdriver.
 Tek dm502 right.jpg
 Tek dm502 leftfront.jpg
@@ Line 38: / Line 44: @@
 Tek dm502 rightfront.jpg
 Tek dm502 rightrear.jpg
-DM502_rear_con.JPG|DM502 rear interface
+DM502_rear_con.JPG | DM502 rear interface – see note above
 </gallery>
-===DM502A===
+==Components==
-<gallery>
+{{Parts|DM502}}
-Tek-dm502a-f.jpg
-Tek dm502a 1.jpg
-Tek dm502a 2.jpg
-Tek dm502a right internal.jpg|DM502A right internal
-Tek-DM502A-rear-interface.jpg|DM502A rear interface
-</gallery>
 [[Category:TM500 multimeter plugins]]
 [[Category:Introduced in 1975]]