Echoes from a distant past
Part four - The Rohde & Schwarz Vacuum Tube Meter URI BN 1050
Edit:
Part one - Siemens Rel. send. 22bPart two - The Two TransformersPart three - The Rohde & Schwarz NGU laboratory power supply unit for vacuum tubesPart four - The Rohde & Schwarz Vacuum Tube Meter URI BN 1050
Part five - The Rohde & Schwarz UVN BN 12001 NF MillivoltmeterPart six - The Nordmende digital multimeter DIVO 3355 (with Nixie tubes!)Hello,
today I'd like to introduce the Rohde & Schwarz URI 1050BN vacuum tube meter which capable of measuring DC volts and currents, AC volts and currents and Ohms. The meter has been produced in the 50's and 60's of the 20th century. It has an impressive wide measurement range. It can measure:
- DC current starting with 2nA up to 1A
- DC voltage starting with 20mV up to 300V (30kV with the 30kV probe)
- AC voltage starting with 0,1V up to 300V (30Hz up to 200MHz)
- AC current starting with 0,1mA up to 1A (30Hz up to 2MHz)
- voltage levels from -20 to +52dB (max. freq. 250MHz)
- Ohms starting from 5Ohm up to 1000MOhm
Let's start with the pictures.
Fastener for the front cover, on top the URI plate with a handle, front view, detailed view of the scale
Detailed view of the beautiful chicken head knobs.
main selector switch, DC ranges, AC ranges
The accessories are stored in the front cover.
overview, 30kV probe, holder for the 30kV probe, corroded banana plug
broken insulation of the 30kV probe, insulation debris, DC voltage probe
RF probe with different hooks, RF-pre-connector divider (plate 1, 2, 3)
Let's see what's inside.
On the right side of the ECC40 there is the voltage reference, a stabilizer tube STV 100/60Z II
Mains transformer, a corroded fuse (mains input terminal), power indicator lamp
back side, bottom side, untouched calibration trimpots, dual diode EB41 with a capacitor bank
nice connection joint, electrolytic capacitors, AEG electrolytic capacitors, vacuum tube socket
And here we are having all the rotary switches.
left ohms switch - mid DC current switch - right DC voltage switch, left AC voltage switch - mid AC current switch - right ohms switch, wirewound resistor mounted on the main selector switch
precision resistors, main range selector switch, detailed view of the ohms range switch,
But how does it perform after all this years?
I took out my Fluke 3330B and did some measures. I used the Brymen BM869s for comparison.
I've warmed up the URI for about 10 minutes before starting the measuring.
And I did of course this null point calibration first as described in the manual.
Because the 3330B can do only DC, no AC measurements were taken.
Lets begin with DC voltage:
1V, 3V, 10V, 30V, 100V, 300V
Voltages are reading a bit low but I haven't checked yet, if they are within specifications.
Next the DC current ranges. The 3330B can do a max current of ca. 111mA, so I'm going to measure only up to the 100mA range.
100nA, 1µA, 10µA, 100µA, 300µA
1mA, 3mA, 10mA, 30mA, 100mA
Some of the DC current ranges are spot on, some are reading a bit high. The 1µA and 100nA range seems to have a problem (needle off the scale). Impressive for an instrument of that age.
Measuring my 10kOhm reference resistor:
I've attached a full scan of the manual here. The source can be found
here.
I hope, you've enjoyed this teardown. Sorry for some of the blurry pictures. It seems, that the camera of my Z3 has come to its limits.
Please stay tuned for part five of this little series, the Rohde & Schwarz NF millivoltmeter UVN BN 12001.
Thank you for watching.
Edit:
I've added the scale in a better resolution (repeated my measures) and added the measuring of my 10kOhm reference resistor.