Re: sensor calibration
 

and that is exactly how it is done, yes Brian
the calibrating inst, the reference std, has a 10 fold greater accuracy (typically); all eventually traceable back to etc.

precisely why I paid $900 for the 2804A, just following normal practice

no cheap zeros (other than BSing)

Re: sensor calibration
 

A bump, because I'm heavily into calibrating my temp transmitters.

http://wbta.us/bigben2k/diffrtdtxm.jpg

The unit:
Moore Industries Temperature transmitter
model RIY/PRG/4-20MA/12-24DC
Specifications
Manual

(great little DIN rail mounted units, I got three, and there are still some available on eBay).

These can be configured for a single RTD (2, 3 or 4 wire) or differential RTD (3 and 2 wires, or 2 and 2 wire).

The LCD display is useless, for my purposes (only shows whole numbers). The output is a 4-20 mA, through the power supply line.

The calibration procedure calls for a "250 ohm precicion resistor, 0.01%" and a decade resistance box, also 0.01%. I'll be trying to replace the box with only the precision resistors that are needed, if I can. As for the 250 ohm resistor, I figure that it only needs to be a known resistor, and doesn't actually need to be of 250 ohm (but should be at least that much).

The resistance values for an RTD are listed here:
http://www.omega.com/temperature/Z/pdf/z252-254.pdf
(NOTE: these are for a 100 Ohm RTD, with an alpha curve of 0.003850, aka European curve)

The units are set at the "zero" and "span" points (i.e. 0% and 100% of full scale). the settings are eeprom'ed.

I'll try to contact the manufacturer, to get a copy of the linearization curve report.

For reference, all three units are set as follows:
Zero: -185
Span: 131
(I have no idea what these numbers represent)

Input: 100 Ohm RTD, alpha 385, range -200 to 850 deg C, accuracy +/- 0.05% of span, +/- 0.20 deg C

I've been going over Groth's frying pan method.:p I expect I'll be putting my Fluke 8840As to work, along with the voltage reference chips.

Re: sensor calibration
 

Hum... that table is pretty useless. Will have to figure out the actual calculation.

The meter shop:
http://www.metershop.com/

Re: sensor calibration
 

hey Bill, any pointers on how I might use and verify this?

http://img.techpowerup.org/060427/MCT.jpg

looks like a calibration standard (might be that type printed on it :p )
and came from Micro Components Technology
of course there isn't any reference to such a minor little device on the site

those are DB15 connectors on each end
and there are just old calibration stickers on the other side


National Cal & Stds LAB (NIST affiliate? some other country's standards lab?)

tag # date (94), due date (95), and

D.B.S./CO134
52 AAA

whatever that means

Id like to first try to "use" it
then see about getting it recalibrated

Re: sensor calibration
 

I believe Bill is no longer posting on these boards (his own choice, he was not banned). You must contact Bill via email or other method.

Re: sensor calibration
 

now why it it semaphore and smoke signals immediately leaped to mind? :p

http://img.techpowerup.org/060427/hey bill.gif


thanx ;)

Re: sensor calibration
 

Because Bill is so old that he actually might know semaphore signalling? :D

Re: sensor calibration
 

well that and he has a thing for native american flag girls :p