AN-78
SS ZMT
General Information
The ZMT Zirconia Indicating Transmitter/Alarm Unit is a
versatile microprocessor based oxygen analyzer designed
primarily to meet the requirements of the boiler market,
utilizing zirconia oxygen probes for energy management.
The ZMT is suitable for use with two types of zirconia oxygen
probe (ZFG2 and ZGP2) and can be provided in standard and
advanced efficiency form.
The standard analyzer has high/low alarms and isolated
retransmission. Display features include probe mV, probe
temperature, cell constant, retransmission range, cell
'warming up' indication with high/low cell fault indication,
thermocouple failure fault indication, a provision to measure
cell impedance, calibration of cell using test gases and the
ability to display a calculated inferred CO
2
value. The standard
unit also accepts inputs of probe mV and thermocouples, with
the facility to program a temperature for use when the probe
has no thermocouple of its own, but the operating temperature
is known.
The standard analyzer provides oxygen readout with
computation based on the probe output voltage. The voltage
output is Nernstian in form and follows the equation:
P
0
E(mV) =
0.0496 T (log
10
––– ) ±C (mV)
P
1
Where
T
=
Absolute temperature (°K)
P
0
=
Partial pressure reference gas
(air)
P
1
=
Partial pressure sample gas
C
=
Cell constant
0.0496 =
Faraday's Gas Constant
The advanced analyzer, in addition to the facilities offered by
the standard analyzer, provides an efficiency calculation
readout by application of the Siegert formula:
K(T
1
– T
2
)
Efficiency =100 – –––––––––
20.8 – %O
2
where T
1
= Flue temperature (at economizer or boiler
output)
T
2
= Inlet air temperature
%O
2
= Measured %O
2
in flue gas
K
= Fuel constant dependent on fuel type
e.g.
Natural gas
K = 0.66
Fuel oil
K = 0.70
Bituminous coal K = 0.73
The efficiency is displayed as a percentage with the facility to
display inlet air temperature and flue gas temperature as
required.
The ZMT can accept a carbon monoxide signal transmitted
from another analyzer unit. This signal can be displayed as
'ppm CO'.
The ZMT compensates for process temperatures in the range
of 600°C to 1400°C (1112° to 2552°F) when used with the
ZGP2 probe. The temperature of the probe heater is
automatically controlled by the ZMT when used with the ZFG2
zirconia probe.
Probe reference air supply is available, either through pump
units or by use of an air regulator operated from the
customer's instrument air line.
Construction and Operation
The ZMT zirconia analyzer is housed in a sheet steel
enclosure, environmentally protected to IP55, having a hinged
front door fitted with a 15 button tactile membrane switch
panel and display window.
There are two blue-filtered, vacuum fluorescent displays
visible through the door window. The upper, five-digit display is
used for monitoring process values. The lower 20-character
dot matrix display is used during setting, operating and
programming.
Membrane switches on the ZMT unit include %O
2
,
temperature, alarm, efficiency, CO
2
/CO and calibration. The
%O
2
, efficiency and CO
2
/CO switches are dedicated push
buttons, i.e. when depressed only the required monitored
value displayed. The units of measurement are indicated on
the dot matrix display.
Temperature, alarms and calibration switches, in conjunction
with the
Å
switch, permit programming and setting up of the
various parameters for system operation. Additional pages
are available through operation of the
É
switch such as the
Analog Retransmission page, the Relay Allocation page,
Diagnostic page and Commissioning page.
Two levels of security are provided to protect various stages of
the programming. The first involves operation of the front
panel switches, the second, more secure, is an internal
switch.
Single fuel and dual fuel boiler operation is monitored by
programmable selections from seventeen different fuel types.
On dual boilers fuel changeover is implemented either
manually of automatically.
The instrument uses a CMOS 6303 microprocessor, a switch
mode power supply with pulse width modulation circuitry for
analog retransmission and offers up to three analog outputs
(isolated) plus up to four relay outputs in combinations of up to
six outputs total.
SUNSTAR传感与控制 http://www.sensor-ic.com/ TEL:0755-83376549 FAX:0755-83376182E-MAIL: [email protected]
SUNSTAR自动化 http://www.sensor-ic.com/ TEL: 0755-83376489 FAX:0755-83376182 E-MAIL: [email protected]
