:-))
Alan
G3NYK
- Original Message -
From: Harry Brownharryhbr...@earthlink.net
To:rich...@karlquist.com; Discussion of precise time and frequency
measurementtime-nuts@febo.com
Sent: Monday, November 15, 2010 7:00 PM
Subject: Re: [time-nuts] Temperature sensors and bridge amps
Back
Harry Brown wrote:
Back in the early 80's I was working for a company making military
communication satellites.
The 5 MHz Oscillators used on the satellite were in a double oven
keeping the oven temp within 0.001 Hz C.
We could adjust the oscillator frequency for aging by ground commanding
Bill Hawkins wrote:
Harry,
What's the ambient temperature swing for the outer oven in space?
Bill Hawkins
That would depend (a lot) on the thermal design of the spacecraft. We
typically design for a temperature range of -20C to +70C, but we don't
expect to see anywhere near that sort
The HP E9183A achieved 1 millidegree over -55 to +85C
in a single oven. The time lag was dealt with by adding
a double integrator to PID.
Rick Karlquist N6RK
On Fri 12/11/10 8:26 AM , Bill Hawkins wrote:
in the heater control loop. Of course, you can't get to a
millidegree from ambient
On 11/13/2010 04:48 PM, Richard Karlquist wrote:
The HP E9183A achieved 1 millidegree over -55 to +85C
in a single oven. The time lag was dealt with by adding
a double integrator to PID.
I'd assume you would intend to write HP E1938A, right?
Cheers,
Magnus
Rick Karlquist N6RK
On
Yes, E1938A. I was operating on limited sleep when I posted that.
Rick
On Sat 13/11/10 8:35 AM , Magnus Danielson wrote:
On 11/13/2010 04:48 PM, Richard Karlquist wrote:
The HP E9183A achieved 1 millidegree over -55 to +85C
in a single oven. The time lag was dealt with by adding
a
Rick,
Is the double integrator actually a cascade of two controllers,
where the primary controls the crystal temperature and its
output sets the setpoint for a heater temperature controller?
That's how industrial control handles the lag between a 5000
gallon reactor and its steam-heated jacket.
Bill,
On 11/14/2010 04:41 AM, Bill Hawkins wrote:
Rick,
Is the double integrator actually a cascade of two controllers,
where the primary controls the crystal temperature and its
output sets the setpoint for a heater temperature controller?
That's how industrial control handles the lag
I understand what you are describing, however, the E1938A
(I typed in the wrong number on the original posting) is
a true single oven. The double integrator is just a
mathematical function in addition to the proportional,
integral, and differential functions that are normally used.
The
One can easily buy 50 PPM/ degree metal film resistors.
You can do much better than that. I don't know how much it matters if the
bridge resistors are mounted near (temperature wise) the sensor.
I poked 10K into Digikey, scrolled down to Resistors, selected through-hole,
and picked 10K
On Thu, 11 Nov 2010 21:38:39 -0800 (PST)
Perry Sandeen sandee...@yahoo.com wrote:
List,
My following comments are am exploratory thought process of which I
don’t profess to know the answers. Perhaps in the future experiments
will provide some.
So here we start.
The Ni1000 SOT
In message 20101112110627.488cb...@vz127.worldserver.net, Florian E. Teply
writes:
In a bridge circuit, you don't measure resistance directly, but use the
voltage that appears across the bridge. So for a 100 ohms element,
you'd usually have ten times the current flowing in that branch
compared
This was one of the things that I wondered about: How large currents are
used ?
Can't be too much because that would lead to self-heating...
I don't know about temperature, but I've worked with load cells. The data
sheet I just found on the web said 350 ohms at 10 V, so 28 mA, or 14 each
Poul-Henning Kamp wrote:
In message20101112110627.488cb...@vz127.worldserver.net, Florian E. Teply
writes:
In a bridge circuit, you don't measure resistance directly, but use the
voltage that appears across the bridge. So for a 100 ohms element,
you'd usually have ten times the current
In message 4cdd1fce.4050...@xtra.co.nz, Bruce Griffiths writes:
Its usually better to use an AC bridge (to minimise the effect of
thermoemfs) or equivalent technique with lower sensor dissipation.
Hehe, I just finished doodleing an idea to use a chopper scheme to
cancel out seebek effects and
Florian E. Teply wrote:
On Thu, 11 Nov 2010 21:38:39 -0800 (PST)
Perry Sandeensandee...@yahoo.com wrote:
List,
My following comments are am exploratory thought process of which I
don’t profess to know the answers. Perhaps in the future experiments
will provide some.
So here we start.
Hi
The 100 ohm standard for RTD's dates way back. The assumption was that you had
it on a *long* run of cable (2 pair / sense leads of course). The insulation
leakage was a bigger issue than anything else in the equation.
Bob
On Nov 12, 2010, at 5:36 AM, Poul-Henning Kamp wrote:
In
On Fri, 12 Nov 2010 10:36:15 +
Poul-Henning Kamp p...@phk.freebsd.dk wrote:
In message 20101112110627.488cb...@vz127.worldserver.net, Florian
E. Teply writes:
In a bridge circuit, you don't measure resistance directly, but use
the voltage that appears across the bridge. So for a 100
As I understand it, the problem to be solved is stability to a
millidegree or some such. That kind of accuracy is not required
because the flat spot of crystal tempco is not narrow. +/- 1%
would be accurate accuracy.
For stability, you must remove all sources of variation. Self-
heating is not a
Why mess with bridges, etc? Analog Devices, among others, make solid state
temperature sensors that are very good and put out linearized currents,
something like 1 mV / Degree K.
-John
===
List,
My following comments are am exploratory thought process of which I
donât profess
IC Instrumentation Amplifiers are very good these days both on offset and
bias currents and voltages. They make bridge amps easy. Gain is selectable
with one resistor.
I still prefer IC sensors though.
-John
===
As I understand it, the problem to be solved is stability to a
List,
My following comments are am exploratory thought process of which I don’t
profess to know the answers. Perhaps in the future experiments will provide
some.
So here we start.
The Ni1000 SOT temperature sensor is a nickel based unit that has a basic
resistance of 1K ohms at 20 degrees C
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