Voltmeter Sch-31 - Nixie Russian Voltmeter

[Rafael]

Hello,

Please, someone can give some tips (or instructions) to use this russian voltmeter?

From the left to right:

MAINS - START - MANUAL - TIME DISPLAY - FILTER

On the selector: WARM UP

and then, CALIBRATOR.

U  --->  V+
U*--->  V-

I and I* appears to be a "Sense" input.

My questions are:

- Warm UP position, should I leave it warming up for 1 hour like modern precisions DMM?

- O1 and O2, are zero1 and zero2?

- Calibration with positions, what I need to do?

Googling deep: https://vk.com/wall396255313_39

Thanks for your help.

?-31

Spasibo

[jeroen79]

I and I* appears to be a "Sense" input.

My guess would be the inputs for current measurements.

[Rafael]

My guess would be the inputs for current measurements.

I will try to see something with a low current...

[MasterT]

My questions are:

- Warm UP position, should I leave it warming up for 1 hour like modern precisions DMM?

- O1 and O2, are zero1 and zero2?

- Calibration with positions, what I need to do?

Spasibo

1. Warm up - 1 hour, there is thermostat. My understanding, temperature 45-50, cooper wire coil as temp sensor, so you can calculate temp in the thermostat know that resistance 10k.
2. O1 - input disconnected, shorted to ground, range 10mV. I'd call - set zero.
   O2 - input connected to 1 MOHm, range 10V. Probably, set full scale.
3. Calibration, range 10V, input connected to precise voltage divider, my guess 1-2-3 etc volts.
Seems dual slope, nothing fancy.

[Gyro]

I and I* appears to be a "Sense" input.

My guess would be the inputs for current measurements.

Looking at how the legs of the resistor symbol are drawn, I think it is likely that they are (also?) used as the current outputs for 4-wire resistance measurement.

Nice meter. 

[Rafael]

1. Warm up - 1 hour, there is thermostat. My understanding, temperature 45-50, cooper wire coil as temp sensor, so you can calculate temp in the thermostat know that resistance 10k.
2. O1 - input disconnected, shorted to ground, range 10mV. I'd call - set zero.
   O2 - input connected to 1 MOHm, range 10V. Probably, set full scale.
3. Calibration, range 10V, input connected to precise voltage divider, my guess 1-2-3 etc volts.
Seems dual slope, nothing fancy.

1 - Right, I will wait for one hour before do something. Ambient temperature is around 23 celsius. Should I connect a copper wire coil in U and U*?

2 - O means Zero? Or some russian word starting with O ?

O1 - I tryed yesterday to short U, U*, I and I*, shows a negative number (-0.000120) responsive to the trimpot, but I reach the end (or start) of the trimpot without reach the absolute zero.

O2 - Should I put a 1MOhm resistor, one lead to U and I, other lead to U* and I* and try to adjust, right?

3 - Can I use a resistor decade?

Looking at how the legs of the resistor symbol are drawn, I think it is likely that they are (also?) used as the current outputs for 4-wire resistance measurement.

Nice meter. 

Yes, I want to see this device working fine...

[MasterT]

1 - Right, I will wait for one hour before do something. Ambient temperature is around 23 celsius. Should I connect a copper wire coil in U and U*?
2 - O means Zero? Or some russian word starting with O ?
O1 - I tryed yesterday to short U, U*, I and I*, shows a negative number (-0.000120) responsive to the trimpot, but I reach the end (or start) of the trimpot without reach the absolute zero.
O2 - Should I put a 1MOhm resistor, one lead to U and I, other lead to U* and I* and try to adjust, right?
3 - Can I use a resistor decade?

1. Temp sensor is Inside a thermostat, you should not do anything except switch to right position. Indication should get stabilized when temp reach equilibrium.
2. No words, zero sign most likely meaning
 If you can't adjust to 0 exact, than device must be re-calibrated or repaired.
1 MOHM - is internal.
3. Divider also is internal, what indicator shows when you rotate a dial?

[Canis Dirus Leidy]

I and I* appears to be a "Sense" input.

It's input for current measuring.

- Warm UP position, should I leave it warming up for 1 hour like modern precisions DMM?

Yes (In normal mode. After repair and parts change it's became more complicated: repair manual (those 200MB pdf file) describes two very long running-in cycles at different environment temperatures).

- O1 and O2, are zero1 and zero2?

Yes, they are for device zeroes adjustment. O1 - voltage zero, O2 - current zero.

- Calibration with positions, what I need to do?

If I correctly understand repair manual it's for use with standard cell (or equivalent voltage source) connected to "Em" sockets on rear panel. "1-10" switch change scaling amplifier gain. Unfortunately, the complete calibration procedure described in "Technical Description" and this document is not available in the Internet.

[Rafael]

Warm UP

Displays are running.

Just power on.

[Rafael]

O2 - Current Zero.
O1 - Voltage Zero.

Display running...

What I need to do to adjust to zero?

I can´t send to repair or calibration... 

I get the impression I saw all the digits lit up yesterday.

[Rafael]

Calibration.

Just numbers running, no matter if 1 or 10 position.

[Rafael]

- H.3. +

Normal Element...

Calibration input?

Seems to be a voltage input.

[Canis Dirus Leidy]

What I need to do to adjust to zero?

Switch the device to the corresponding mode and adjust potentiometer (slotted screws on front panel). Warning: these settings are interdependent, so the zero setting for each mode will have to be repeated several times.

Just numbers running, no matter if 1 or 10 position.

Well, if calibration input has remained unconnected then device "measure" some noise on amplifier output.

Normal Element...
Calibration input?

This. Try to connect some DC voltage source (and set gain value so that the resulting voltage was no more than 10V) and see if there any sane result.

[Rafael]

What I need to do to adjust to zero?

Switch the device to the corresponding mode and adjust potentiometer (slotted screws on front panel). Warning: these settings are interdependent, so the zero setting for each mode will have to be repeated several times.

Right, but I need to short U, U*, I and I* or all front panel inputs? GND, U, U*, I, I* and 1Kv?

When you say: "repeated several times", what I think:

Find zero in position O1 and O1 using potentiometers, then, put the switch to, for example, 10V and find again. Or each time that I turn on the voltmeter?

Just numbers running, no matter if 1 or 10 position.

Well, if calibration input has remained unconnected then device "measure" some noise on amplifier output.

Normal Element...
Calibration input?

This. Try to connect some DC voltage source (and set gain value so that the resulting voltage was no more than 10V) and see if there any sane result.

It seems clear, I will try to do this.

Thanks for the explanation and patience.

[Canis Dirus Leidy]

Right, but I need to short U, U*, I and I* or all front panel inputs? GND, U, U*, I, I* and 1Kv?

If you switch to O1/O2 mode then all the necessary commutations (plus bypassing amplifier) are done automatically.

When you say: "repeated several times", what I think:
Find zero in position O1 and O1 using potentiometers, then, put the switch to, for example, 10V and find again. Or each time that I turn on the voltmeter?

I meant that adjusting zero in one mode disturb adjustment made in other mode. So zero setting algorithm look like this:

• Switch to O1 mode. Adjust zero.
• Switch to O2 mode. Adjust zero.
• Switch back to O1 and repeat until setting up zeroes in both modes

[Rafael]

Right, but I need to short U, U*, I and I* or all front panel inputs? GND, U, U*, I, I* and 1Kv?

If you switch to O1/O2 mode then all the necessary commutations (plus bypassing amplifier) are done automatically.

Looks an amazing device.
If I don't need to short inputs, I need to do another adjustment to reach zero? I mean, on the top of the device, there are potentiometers, untouched potentiometers, I need to do some adjustment?

Thanks

[Canis Dirus Leidy]

If I don't need to short inputs, I need to do another adjustment to reach zero? I mean, on the top of the device, there are potentiometers, untouched potentiometers, I need to do some adjustment?

In the norm - no. These trimmers are intended for assembly (Device was designed in seventies. What is mean discrete components and a lot of manual adjustment) and service technicians.

[Rafael]

Well.

According to the instructions, I was able to better understand how this excellent machine works.

1 - The selector must be in the "warm up" position. A negative number will start to run fast (-00.83000) and then, around one hour, this incremental number will run slow, very slow (-00.94000) until you see this "race" becomes very slow, giving the impression of not running anymore. I understand that the device is ready!

2 - In O2 position, it´s possible to adjust the potentiometer until you see (+000000) alternating with (-000000), for me, the voltage zero is done.

3 - In O1 position, it´s not easy to set the zero, but something near of it, by the speed of variation between (+000065) and (-000050).

4 - Checking again O2, need a small adjustment again.

5 - Checking again O1, another small adjustement back to 4 until you a balance between the two settings. At this point, nothing is connected to the inputs.

6 - Calibration position, I started with a voltage of 2.5V and saw in the display: (+1.020000), so I turned the dial from 1 to 10, nothing changed. I understood that for this calibration, it is necessary, through the back connectors, the voltage of 1.0V.

7 - I put 1V and I understood that the selector was just a fine adjustment, for example: If the selector is in position 5, adjust the potentiomentro to exact 1.000000v, in position 6 it will be 1000100v, in position 7 will be 1,000200ve in position 4 will be 0.000900v. It is as if the selector was a fine adjunct, some actuation of the amplifier to hit the input voltage.

I have two challenges ahead: I need to make a connector with probe cables, I thought of making a board that fit perfectly in the connectors and with a selector switch for 1kV and another to connect U with I and U * with I *. The other challenge is to make a stable reference of 1.000000v.

Attached, some images.

Spasibo!!

 

[Rafael]

More images... 

[Rafael]

Thanks!