Super Systems Gold Probe User Manual

Gold Probe

Instructions Manual

7205 Edington Drive

Cincinnati, OH 45249

513-772-0060 800-666-4330

Fax: [phone]

www.supersystems.com

INTRODUCTION .................................................................................................................... 2

SPECIFICATIONS.................................................................................................................. 2

CHARACTERISTICS .............................................................................................................. 3

BASIC OPERATING THEORY ................................................................................................ 4

INSTALLATION ..................................................................................................................... 5

MAINTENANCE .................................................................................................................... 6

Table of Contents

Furnace conditioning ........................................................................................................ 6

Probe conditioning: ........................................................................................................... 7

TROUBLE SHOOTING ........................................................................................................... 8

Probe troubleshooting: ..................................................................................................... 8

CONTROL SYSTEMS ............................................................................................................. 9

WARRANTY ......................................................................................................................... 11

NOTES ................................................................................................................................ 12

CARBON vs. DEW POINT WITH TEMPERATURE ............................................................... 13

CARBON vs. MILLIVOLTS WITH TEMPERATURE .............................................................. 14

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 Useful %C Range- .01 to 1.6%

 Temperature Range- 1200F to 2000F

(649C to 1093C)

 Stability- within +/- 1 mVDC

 Impedance- less than 10 kohms @ 1700F

(927C)

 Mounting- 1" (25.4mm) NPT

 Sheath dia.- 0.84" (1/2" pipe)

(21mm, 13mm pipe)

 Useful output- 0 to 1250 mVDC

Probe Specifications

Model

Nominal Insertion

Length

Nominal Overall Length

Boxed Weight

INCHES

MILLIMETERS

INCHES

MILLIMETERS

POUNDS

KILOGRAMS

GP133

14.3

364.0

20.8

528.0

3.6

1.8

GP205

20.5

521.5

27.2

690.0

4.0

1.8

GP277

27.7

705.0

34.3

871.0

4.6

2.1

GP330

33.0

840.0

39.5

1003.0

5.4

2.4

GP373

36.8

936.5

43.4

1101.5

5.8

2.6

GP420

42.0

1069.0

48.3

1228.0

6.4

2.9

GP480

48.0

1221.5

54.3

1379.5

6.8

3.1

INTRODUCTION

SPECIFICATIONS

Thank you for selecting the Gold Probe™ for your atmosphere control application.

The Gold Probe™ represents “state of the art” in carbon sensor technology. It has been

designed for use in carbon control systems as applied to both carbon control in
atmosphere furnaces and dew point in endothermic generators.

The Gold Probe™, with its unique measuring electrode construction, is the product of a

team of design and application engineers, each with over twenty years of atmosphere
control experience. The SSi engineering team has long recognized that the sensor is the
most critical component in the atmosphere control system and has traditionally been
the weakest link. Now, reliability, repeatability and accuracy are assured with the
inclusion of the Gold Probe™ in

your

control system.

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CHARACTERISTICS

The typical zirconia carbon sensor consists of a
closed end tube with the sensing portion at the tip.
The entire tube may be zirconia or there may be a
slug of zirconia cemented in the tip. Fig.1
illustrates the Gold Probe™ design with details
omitted for clarity. The tip of the tube is spring
loaded into contact with the sheath, which also
serves as the outer electrode. The inner electrode
is spring loaded into contact with the inner
zirconia surface. A thermocouple is positioned
close to the inner electrode surface and reference
air bathes the sensing surface.

To the instrument technician, the probe looks like
a battery (see Fig.2.) It displays a voltage, Ec, from

which the carbon potential can be calculated. The
probe thermocouple is shown next to the sensing
electrode.

The value of the internal resistance can be
measured, as shown in Fig. 3, by putting a shunt
resistor across the probe, measuring the resultant
voltage, Em and carrying out the simple calculation

shown.

FIG. 1

FIG. 2

FIG. 3

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BASIC OPERATING THEORY

Carbon potential of a conventional furnace
atmosphere is defined as the %C achieved in a
coupon of carbon steel shim stock equilibrated in
the furnace atmosphere. Unfortunately,
equilibration time is long, so it is impossible to
continuously control the atmosphere on the
basis of shim stock measurements. A zirconia
sensor, however, can be used to measure and
control the carbon potential precisely, and on a
continuous basis.

Strictly speaking, the zirconia probe is not
sensing carbon at all. It is an oxygen sensor with
a mVDC output described by Equation (1).

Fortunately, an empirical (experimental)
relationship exists between oxygen
concentration and carbon potential, and this
relationship has been used in carbon control

instruments since the early ‘70’s. The equation

used by most control manufacturers today is
illustrated by Equation (2), which states that
there are only

three

variables affecting the
measured millivoltage. Because the actual
equation used is somewhat complex, it is not
reproduced here. A full description of probe
theory will be found in SSi technical bulletin
T4401 (Zirconia Sensor Theory).

All

competitive probes will invariably agree
within one or two millivolts when exposed to the
same atmosphere under equilibrium conditions.
Differences in values listed by probe vendors

relate to differences in manufacturers’ source

data, but the true value of the zirconia probe is
its repeatability.

ZIRCONIA O2 RESPONSE

Ec = 0.0276TR log (Pf /Pa) millivolts (1)

Zr PROBE ALGORITHM

%C= ( EC , %CO, TR) mVDC (2)

Where: means ‘is a function of’

%C is the carbon potential

%CO is carbon monoxide percentage

TR is the absolute temperature in

degrees

Rankine (deg. F + 460).

and EC is the probe output in millivolts.

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