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The nanodac recorder/controller provides combined recording and
control in a single ¼ DIN package.
There are two control loops. In this application only one of these loops is
used to control the temperature. A Zirconia probe is used to measure the
level of oxygen and Virtual channels are configured to display the
measured values.
The nanodac recorder/controller can accommodate a range of probes
from various manufacturers. A suitable probe is the Eurotherm ECprobe
which is interchangeable with all other carbon sensors. It is available in
600mm or 900mmm lengths with or without integral thermocouple in
types K, N, S, or R. A typical orde r code is CP600-K.
Purpose of this note
The purpose of this application
note is to describe how the
nanodac recorder/controller may
be used to measure oxygen
levels and control temperature in
metal heat treatment furnaces.
Using the measurements of
oxygen level and temperature the
nanodac recorder/controller may
also be used to calculate the
carbon potential levels using the
Zirconia function block.
The nanodac recorder/controller
may also be used to measure
oxygen levels, for example in
chimney stacks.
Heat/Cool with Carbon Potential or
Oxygen Level Monitoring using the
nanodac Recorder/Controller
Application Note
nanodac™
Recorder/Controller
MODEL
Application Example
Channel 1 thermocouple input.
Loop 1 heat/cool control. The heating channel is a time
proportioning logic output used to drive a solid state relay
or thyristor unit. The cooling channel uses a relay output,
which in an oven application, would probably operate a
cooling fan.
The loop wSP and wOP are charted using virtual channels.
The Zirconia block measures both oxygen and temperature
using input channels 2 and 3 respectively and a third virtual
channel is used to chart the level of oxygen.
Eurotherm Part No. HA030817U002 Issue 1 September 10 2 nanodac Application Note
Heat/Cool with Carbon Potential or Oxygen Level
Monitoring using the nanodac Recorder/Controller
Introduction
When mild steels or certain low carbon steels are heated at
temperatures above 900°C in a carbon rich atmosphere
the surface of the steel absorbs carbon by diffusion. The
depth of carbon enrichment depends on the time and
temperature of the treatment known as carburising. The
presence of carbon in the steel causes a change in its
physical properties.
A Zirconia probe is used to measure the level of oxygen. It
generates a millivolt signal based on the ratio of oxygen
concentration between the reference airside of the probe
(outside the furnace) and the amount of oxygen actually
inside the furnace.
The temperature of the furnace is measured using a
thermocouple. This may be a thermocouple mounted
within the Zirconia probe or installed as a separate item.
Together the temperature and oxygen level signals are
used by the nanodac recorder/controller to calculate the
actual percentage of carbon in the furnace atmosphere.
Furnace
Thermocouple
Screen
Thermocouple
Zirconia pellet
Outer
electrode
Inner
electrode
Heating
SSR
Cooling
Fan
3B
3A
N
L
2B
2A
1B
1A
LC
LA
2I
1–
1+
1I
2–
2+
4I
3–
3+
3I
4–
4+
I/O1
OP2
OP3
DIA
C
4A
LC
LB
E
5A
Physical Wiring