BACKGROUND OF THE INVENTION
[0001] The present invention relates to an improved method and apparatus for improving the
efficiency of gas appliances.
[0002] Gas appliances such as water heaters, floor heaters, space heaters, room heaters,
boilers, central furnaces, clothes dryers and cooking ranges, have gained wide acceptance
with the consuming public. Conventional gas heating appliances typically employ manually
operated gas valves to regulate and control gas flow to burners for combustion to
generate heat from the burning of natural or propane gas.
[0003] The fixed orifice in a conventional gas valve, however, is not capable of continuous
active adjustment of pressure and flow rate of gas into the burner resulting in inefficient
combustion, i.e., too little heat and too much exhaust generated from a gas-heating
appliance.
[0004] Excessive gas flow with inadequate air in the combustion mixture, or vise versa,
will cause less heat and excess exhaust. Moreover, various ambient conditions such
as altitudes in different parts of the world, are variable factors that can contribute
to combustion efficiency. The components of conventional gas heating appliances are
generally fixed and not self-adjusting to account for these various ambient conditions.
[0005] Those skilled in the art have recognized a significant need for a variety of control
systems that improved the efficiency of the fuel combustion of gas appliances.
[0006] U.S. Patent No. 6,398,118 issued to Rosen, et al., discloses a system for monitoring and modifying the quality and temperature of air
within a conditioned space including a blower unit, a damper unit for selectively
admitting outside air into the conditioned space, a temperature moderating unit and
a control unit.
[0007] The Rosen system relates to the art of conditioning indoor living and working and
other enclosed public spaces. More particularly, the patent discloses a system in
which the carbon dioxide (CO
2) level is monitored and controlled by apparatus in which the CO
2 sensor and support circuitry is integral with a thermostat which also serves to conventionally
control the temperature range within the conditioned space.
[0008] The principle of operation of the CO
2 sensor is stated to be that, the cell constituting the cathode, anode and solid electrolyte,
becomes susceptible to readily measurable change in accordance with the CO
2 concentration at the cell. This known effect appears to be due to a chemical reaction
between the CO
2 and the electrolyte which must be selected to enhance the extent of the change in
accordance with the gas of interest. Combinations of electrodes and electrolytes suitable
for the purpose are discussed, for example, by
S. Azad, S.A. Akbar, S.G. Mhaisalkar, L.D. Birkefeld and K.S. Goto in the Journal
of the Electrochemical Society, 139, 3690 (1992). One suitable combination, which gives very good results for measuring CO
2 concentration is: platinum (Pt) for the cathode, reference electrode 30; silver (Ag)
for the anode, sensing electrode 31; and a mixture of Na
2 CO
3, BaCO
3 and AG
2 SO
4 as the solid electrolyte.
[0009] U.S. Patent No. 6,286,482 issued to Flynn, et al., discloses a premixed charge compression ignition engine, and a control system, which
effectively initiates combustion by compression ignition and maintains stable combustion
while achieving extremely low oxides of nitrogen emissions, good overall efficiency
and acceptable combustion noise and cylinder pleasures. The Flynn engine and control
system effectively controls the combustion history, that is, the time at which combustion
occurs, the rate of combustion, the duration of combustion and/or the completeness
of combustion, by controlling the operation of certain control variables providing
temperature control, pressure control, control of the mixture's autoignition properties
and equivalence ration control. The combustion control system provides active feedback
control of the combustion event and includes a sensor, e.g. pressure sensor, for detecting
an engine operating condition indicative of the combustion history, e.g. the start
of combustion, and generating an associated engine operating condition signal. A processor
receives the signal and generates control signals based on the engine operating condition
signal for controlling various engine components to control the temperature, pressure,
equivalence ration and backlash or autoignition properties so as to variably control
the combustion history of future combustion events to achieve stable, low emission
combustion, in each cylinder and combustion balancing between the cylinders.
[0010] The Flynn patent discloses a strategy for controlling the start and direction of
combustion by varying the air/fuel mixture autoignition properties. The autoignition
properties of the air/fuel mixture may be controlled by injecting gas, e.g. air, oxygen,
nitrogen, ozone, carbon dioxide, exhaust gas, etc., into the air or air/fuel mixture
either in the intake system.
[0011] U.S. Patent No. 6,392,536 issued to Tice, et al. discloses a multi-function detector which has at least two different sensors coupled
to a control circuit. In a normal operating mode the control circuit, which would
include a programmed processor, processes outputs from both sensors to evaluate if
a predetermined condition is present in the environment adjacent to the detector.
In this mode the detector exhibits a predetermined sensitivity. In response to a failure
of one of the sensors, the control circuit processes the output of the remaining operational
sensor or sensors so that the detector will continue to evaluate the condition of
the environment with substantially the same sensitivity.
[0012] U.S. Patent No. 5,644,068 issued to Okamoto, et al. discloses a gas sensor of the thermal conductivity type suitable for the quantitative
analysis of the fuel vapor content of a fuel-air mixture. The Okamoto gas sensor comprises
a sensing element and a compensating element, each of which includes an electrically-heated
hot member incorporated into a Wheatstone bridge circuit powered by a constant current
supply circuit. The constant current supply circuit is adjusted and regulated such
that the hot member of the sensing element is heated with an electric current of such
an intensity that corresponds to a point of transition (Y) at which, at the interface
of the hot member and the mixture, the predominant mode of heat transfer changes from
thermal conduction to natural convection.
[0013] The disclosures of the foregoing patents are hereby incorporated by this reference.
[0014] While recognizing the advantages of control systems utilizing exhaust gases as possible
parameters to improve efficiency, these systems do not provide the critical recognition
of exhaust gas concentration levels, such as carbon dioxide, for continuous active
feedback control of future combustion evente. The present invention achieves these
goals.
SUMMARY OF THE INVENTION
[0015] A unique control system is provided for optimizing and for effecting efficient combustion
of gas appliances by controlling the proportion of fuel and air variables. The combustion
control system provides continuous active feedback control of the combustion event
by detecting the level of exhaust gases such as CO
2 within a prescribed optimum range. The system comprises a qualitative and quantitative
sensor and processor to trigger the modulation of a valve to adjust pressure and gas
flow to combustion chamber of gas appliance, when the concentration of the detected
gas falls outside the prescribed optimum range. Accordingly, the control signal varies
the proportion of air to fuel inflow to a prescribed optimum range for future events
thereby achieving efficient fuel combustion.
[0016] The present invention achieves improved combustion efficiency by adjustment of pressure
and fuel flow related to changing ambient conditions. In a presently preferred embodiment,
the inventive system comprises a CO
2 sensor to continuously measure the concentration level of carbon dioxide of the combustion
chamber. The sensor generates a signal, including detected qualitative and quantitative
measurements, that is received by a microprocessor. The processor, in turn, compares
the received sensor signal with prescribed levels, and determines whether to adjust
a pressure regulator of a gas valve to bring the air/fuel mixture to a prescribed
optimum range for future combustion events.
[0017] In one embodied form, the system comprises active feedback control means based upon
detection of the concentration of carbon dioxide. Assuming fixed exhaust gas flow
from combustion, the prescribed concentration level of carbon dioxide gas for optimum
efficiency is within a range of about seven and one half percent (7.5%) to about eight
percent (8%). Accordingly, if for example, the sensor detects a concentration level
of nine percent (9%) carbon dioxide, the control means will accordingly decrease the
air flow into the burner of the gap appliance. If the concentration of carbon dioxide
in the exhaust gas is less than seven percent (7%), the control means will proportionately
increase the intake air flow to the combustion chamber. Thus greatest combustion efficiency
can be achieved by monitoring and maintaining the concentration of carbon dioxide
within the prescribed range.
[0018] In a second embodiment, the inventive system comprises a CO
2 sensor, CO sensor, O
2 sensor to trigger the modulation of gas valve to adjust pressure of gas pressure
and gas flow to combustion chamber of gas appliance. In operation, modulation will
take place, should the detected carbon dioxide concentrate within the gas mixture
falls outside a specified range of concentration. Modulation of the inventive gas
valve can be to such an extent to minimize gas flow to future combustion events.
[0019] The inventive system comprises a processor that receives the qualitative and quantitative
signal from the carbon dioxide sensor and provides feedback control to an electronic
control unit (ECU). ECU receives the sensor signal and processes the signal to determine
the appropriate adjustment, if any, to the flow of air to be mixed with fuel for combustion
in the burner unit. The signal reflecting the carbon dioxide concentration in the
exhaust gas is then compared to a predetermined database of desired airflow adjustment
values. Based on the comparison of the actual airflow to the desired airflow adjustment
value, the ECU then generates a plurality of output signals, for variably controlling
a pressure regulator of a gas intake flow valve and other respective components of
the system so as to effectively ensure, that the future carbon dioxide concentration
in the exhaust gas is maintained within the prescribed optimum range.
[0020] The combustion control scheme is most preferably implemented in software contained
in ECU that includes a central processing unit such as a micro-controller, micro-processor,
or other suitable micro-computing unit. Accordingly, the unique system achieves high
efficiency combustion in a wide variety of gas heating appliances.
BRIEF DESCRIPTION OF THE DRAWING
[0021] Figure 1 is a cross-sectional side view of one embodied CO
2 sensor and Pitot tube in accordance with the present invention.
[0022] Figure 2 is a side sectional view illustrating the system components and placement
of a CO
2 sensor in the control processor in accordance with the present invention.
[0023] Figure 3 is a schematic sectional view depicting a gas valve in accordance with one
embodied form of the invention.
[0024] Figure 4 is a schematic flow chart indicating the components and interaction of the
high efficiency fuel injection system for gas appliances in accordance with the present
invention;
[0025] Figure 5 is a schematic flow diagram of one embodied form of the inventive system
and further indicating the levels of CO
2 detected to activate the modulation of the inventive gas valve to adjust pressure
and flow of gas to the combustion chamber in accordance with one embodied form of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] A unique control system is provided for gas appliances to achieve efficient combustion
by controlling the proportion of fuel and air variables. The combustion control system
provides active feedback control of the combustion event and includes a CO
2 to trigger the modulation of a gas valve to adjust pressure of gas pressure and gas
flow to combustion chamber of gas appliance. Detection of other combustion gases such
as carbon monoxide and oxygen may also be utilized by the system, with carbon dioxide
gas being the principal gas for triggering the modulation of the gas valve. A microprocessor
receives the concentration signals from the sensors and generates control signals
based on the concentration signal for controlling a pressure regulator of the gas
valve so as to variably control future combustion events to achieve maximum fuel combustion
efficiency. Accordingly, the control signal varies the proportion of air to fuel inflow
to a prescribed optimum range achieving efficient fuel combustion.
[0027] In a presently preferred embodiment, the present invention provides an improved method
and apparatus for achieving high efficiency of combustion by comprising active feedback
control means based upon detection of the concentration of carbon dioxide within the
prescribed optimum range of about 7.5% to about 8.0%. Assuming fixed exhaust gas flow
from combustion, if the concentration level of carbon dioxide exceeds about nine percent
(9%), the control means will accordingly decrease the air flow into the burner of
the gas heating appliance. If the concentration of carbon dioxide in the exhaust gas
is less than seven percent (7%), the control means will proportionately increase the
intake air flow to the combustion chamber. Thus greatest combustion efficiency can
be achieved by monitoring and maintaining the concentration of carbon dioxide within
the prescribed range.
[0028] In a second embodiment, the inventive system comprises a CO
2 sensor, CO sensor, and O
2 sensor to trigger the modulation of gas valve to adjust pressure of gas pressure
and gas flow to combustion chamber of gas appliance. In operation, modulation will
take place if the CO
2 content of the gaseous mixture falls outside the prescribed range of concentration.
For instance, in the case of CO
2, modulation is within the range of 7 percent to 9 percent. Gas pressure and flow
will be adjusted in responding to changes of concentration, before CO
2 reaches 7 percent or 9 percent. Actually, modulation of gas value can be to such
an extent to minimize gas flow.
[0029] The sensor module provides a O-4VDC output scaled to 0-2000 ppm CO
2. The sampling method for detection of the carbon dioxide concentration may be wither
flow through or diffusion and can be configured to measure ppm levels up to 5%. The
modules include self-calibration algorithm that eliminates the need for on-going calibrations.
[0030] The CO sensor is operational to trigger the modulation of gas valve to lower the
amount of gas flow to combustion chamber of gas appliance. If the concentration is
less than 65 PPM, the sensor is not activated. Preferably, the CO sensor accumulates
concentration up to 65 PPM of carbon monoxide in one hour.
[0031] The O
2 sensor is operational to trigger the modulation of gas valve to lower the amount
of gas flow to combustion chamber of gas appliance. If the level is over 19.5 percent,
the sensor is not activated.
[0032] The system may use conventional shut off mechanims for instance disclosed in
US Patent No. 5838243, which is hereby incorporated by this reference.
[0033] After generating the sensor concentration signal, the control processor will determine
the desired adjustment of air inflow by setting the pressure regulator of a gas valve
to a prescribed optimum range.
[0034] The modulating gas valve will preferably comply with applicable industry and governmental
standards. e.g. AGA Requirements for automatic, non-shutoff modulating gas valves
No. 1-92 (1992) which is hereby incorporated by this reference.
[0035] This standard applies to produced automatic modulating valves, herein after referred
to as valves, hereinafter referred to as valves, and the valve control system, constructed
entirely of new, unused parts and materials. These valves may be individual valves,
valves utilized as parts of automatic gas ignition systems, or the modulating valve
functions of combination controls.
[0036] These valves are intended to be used to vary the gas input rate to the appliance,
as a function of the signal from the gas valve control system. These valves are not
intended to provide for complete shutoff of the gas flow to the main burners.
[0037] Those skilled in the art will recognize that the inventive system is capable of activation
and modulation by detection of carbon dioxide levels, within a prescribed range of
from about 6% to about 10%.
[0038] The following summary provides the modulation parameters to improve combustion efficiencies:
Activation:
[0039]
- Range of sensor between about 6% to 10% of CO2 concentration
- .5% of CO2 changes would activate gas control to modulate outlet pressure by .36" W.C. to .39"
W.C.
- If 9% of CO2 by the sensor, gas control would modulate pressure downward to 2.87" W.C. from 4.0"
W.C.
- If 6.5% of CO2 by the sensor, gas control would modulate pressure upward to 4.25" W.C. from 4.0"
W.C.
[0040] Typically, the mechanisms of valves will be protected by substantial enclosures so
as to prevent interference with the safe operation of the devices.
[0041] Pins, stems, or other linkage passing through the valve body or casing shall be sealed
to provide gastight construction.
[0042] Diaphragm type automatic valves in which a flexible nonmetallic diaphragm constitutes
the only gas seal and which utilise control gas on the atmospheric side of the diaphragm
shall have the atmospheric side of the main diaphragm enclosed in a gastight casing
with means provided for bleeding the control gas.
[0043] Valves in which a flexible nonmetallic diaphragm constitutes the only gas seal shall
have the atmospheric side of the diaphragm enclosed to limit the leakage to atmosphere
in the event of diaphragm rupture to not more than 1.0 cubic foot per hour at the
maximum pressure rating of the valve when tested with a gas having a specific gravity
of 1.55 or shall be provided with means for venting the gas in the event of diaphragm
rupture.
[0044] The CO
2 Sensor module communicates over an synchronous, UART interface at 9600 baud, no parity,
8 data bits, and 1 stop bit. When the host computer of PC communicates with the sensor,
the host computer sends a request to the sensor, and the sensor returns a response.
The host computer acts as a master, initiating all communications, and the sensor
acts as a slave, responding with a reply.
[0045] Preferably, sensor commands and replies are wrapped in a secure communications protocol
to insure the integrity and reliability of the data exchange. One suitable communications
protocol for the serial interface and the command set for the module CO
2 Sensor are set forth below.
[0046] Each command to the sensor consists of a length byte, a command byte, and any additional
data required by the command. Each response from the sensor consists of a length byte
and the response data if any. Both the command to the sensor and the response from
the sensor are wrapped in a communications protocol layer.
Command: <length><command>additional_data>
Response: <length><response_data>
[0047] The communications protocol consists of two flag bytes (0xFF) and an address byte
as a header, and a two-byte CRC as a trailer. In addition, if the byte 0xFF occurs
anywhere in the message body or CRC trailer, the protocol inserts a null (0x00) byte
immediately following the 0xFF byte. The inserted 0x00 byte is for transmission purposes
only, and is not included in the determination of the message length or the calculation
of the CRC.
Header |
Message Body |
Trailer |
<flag><flag><address> |
<Command/Response> |
<crc_Isb><crc_msb> |
[0048] When receiving a command or response, the flags and any inserted 0x00 bytes must
be stripped from the message before calculating the verification CRC. A verification
CRC should be computed on all received messages from the sensor and compared with
the CRC in the massage trailer. If the verification CRC matches the trailer CRC, then
the data from the sensor was transmitted correctly with a high degree of certainty.
[0049] In response to the concentration signal from the sensor module the air flow from
a gas valve will be adjusted by pressure regulator before it flows to burner, prior
to combustion chamber. If concentration of carbon dioxide is more than 9 percent (9%),
gas flow will be adjusted upward to increase its mixture with air, and if concentration
of carbon dioxide is less than 7 percent (7%), gas flow will be adjusted downward
to decrease its mixture with air.
[0050] Figure 4 is a schematic flow chart indicating the components and interaction of the
high efficiency fuel injection system for gas appliances in accordance with the present
invention;
[0051] Figure 5 is a schematic flow diagram of the inventive system and further indicating
the levels of CO
2 detected to activate the modulation of the inventive gas valve to adjust pressure
and flow of gas to the combustion chamber in accordance with one embodied form of
the present invention.
[0052] In the CO
2 module, a bus interfaces to both an external processor and the A/D converter which
is collecting the CO
2 data. When the module is collecting data, its serial shift clock is configured to
generate its own internal clock. That is, the module is said to be operating in "master"
mode. When the CO
2 module is communicating with an external processor, it relies upon the external processor
to supply the clock pulse, called the "slave" mode.
[0053] Thus, to an external process, the CO
2 module appears as a slave on the bus. The external processor is the master, meaning
that it provides the SK clock signal for both sending and receiving data across the
bus. From the CO
2 module's point of view, during communications with an external processor, is SI (serial
in) and SK (serial clock) are inputs, and its SO (serial out) is an output. Additionally,
there are two digital handshake lines that an external processor uses to communicate
with the CO
2 module.
[0054] Every data exchange between an external processor and the CO
2 module starts with the external processor sending a request data-packet--several,
bytes--to the CO
2 module. The CO
2 module then responds by returning a response data-packet to the external processor.
The request data packet contains a command byte, and perhaps one or more parameter
bytes.
[0055] After receiving each byte in a request data packet, the CO
2 module raises the UB_ACK handshaking line. When it is ready to receive the next byte
it lowers UB_ACK. The external processor must send the next byte to the CO
2 module within 10 milliseconds from the time the UB_ACK line goes low. This handshaking
between bytes provides flow control and insures that the external processor does not
overrun the CO
2 module's input buffer and that the CO
2 module does not wait indefinitely for the external processor to send the next byte.
After receiving the final byte of the request data-packet, the CO
2 module again raises UB_ACK.
[0056] When the CO
2 module has processed the request and is ready to send the first byte of the response
data-packet, the CO
2 module lowers UB_ACK. The external processor has 10 milliseconds from the time the
UB_ACK lines goes low in order to start the clock and receive the byte. After transmitting
the byte, the CO
2 module raises UB_ACK, and lowers it again when it is ready to transmit the next byte.
The process continues until all bytes of the response data-packet have been transmitted
to the external processor. The 10 millisecond time limit insures that the CO
2 module does not wait indefinitely for the external processor to start the clock to
receive the byte.
[0057] After sending the final byte in a response, the CO
2 module raises UB_ACK and leave it high. The external processor then raises UB_REQ,
concluding the data interchange. UB_REQ must stay high longer than a specified minimum
before the external processor lowers it to start the next data exchange.
[0058] At the conclusion of a response data packet, the CO
2 module will wait approximately 100 milliseconds after the final UB_ACK goes high
before initiating its return to master mode and the resuming of data collection. If
the external processor raises and lowers UB_REQ during this delay interval, the module
stays in slave mode and immediately services the new request. The delay interval gives
the external processor the opportunity to send a series of commands in rapid succession
to the module. Note that the CO
2 module is not functioning as a sensor while it is in the slave mode.
[0059] The raising of UB_REQ, together with the expiration of the delay time interval, is
the signal to the CO
2 module to return to Microwire master mode and resume its A/D converter data collection.
Microwire mode conversion and re-initialization for data collection is a time consuming
process, and the module has only three opportunities during the process to abort and
respond to a new UB_REQ. Hence, for non-PPM/Temperature request, it is most time-efficient
to start the next UB-REQ during the delay interval following the previous request.
[0060] If the external processor needs to terminate an incomplete data exchange it raises
the UB_REQ line. When the CO
2 module see this, it discards the contents of its communication buffers and then respond
by raising the UB_ACK.
[0061] If the CO
2 module needs to terminate an incomplete data exchange, it raise UB_ACK. If UB_ACK
remains high longer than the maximum time specified for UB_ACK High Between Bytes,
then the external processor must recognize this as termination of an incomplete data
exchange. For example, if the CO
2 module receives bytes that do not correspond to a valid request data-packet then
it raises UB_ACK and holds it high, signaling termination of an incomplete data exchange.
[0062] The CO
2 module starts a 10 millisecond timeout timer each time it lowers UB_ACK. The external
processor must respond by starting the serial shift clock within this interval so
that the module can transmit or receive the pending byte. If the external processor
fails to start the clock, the CO
2 module presumes that the communication has been aborted and will raise UB_ACK.
[0063] If either the external processor or the CO
2 module terminates a data exchange, no new communication can be initiated until both
UB_ACK and UB_REQ have return to the high state. The new command then starts with
the external processor lowering UB_REQ as described above.
[0064] The inventive system comprises a processor that receives the qualitative and quantitative
signal from the carbon dioxide sensor and provides feedback control to an electronic
control unit (ECU). ECU receives the sensor signal and processes the signal to determine
the appropriate adjustment, if any, to the flow of air to be mixed with fuel for combustion
in the burner unit. The signal reflecting the carbon dioxide concentration in the
exhaust gas is then compared to a predetermined database of desired airflow adjustment
values. Based on the comparison of the actual airflow to the desired airflow adjustment
value, the ECU then generates a plurality of output signals, for variably controlling
a pressure regulator of a gas intake flow valve and other respective components of
the system so as to effectively ensure, that the future carbon dioxide concentration
in the exhaust gas is maintained within the prescribed optimum range.
[0065] The combustion control scheme is most preferably implemented in software contained
in ECU that includes a central processing unit such as a micro-controller, micro-processor,
or other suitable micro-computing unit. Accordingly, the unique system achieves high
efficiency combustion in a wide variety of gas heating appliances.
[0066] The following example provides the presently preferred parameters for achieving high
efficiency combustion:
EXAMPLE
General
[0067]
- 02 reaches 18.2%, CO is present dangerous level of 80PPM per hour. In testing, 18%
of O2, CO detector still shows 43PPM per hour.
- Accuracy of CO sensor alone, without CO2 sensor) cannot be counted for real application.
- Monitoring CO2 concentration is preferred to measure and monitor for combustion efficiency
of a gas heating appliance.
Function Required for Gas Control
[0068]
- Range of Regulation; minimum 20,000 BTU per hour, maximum 200,000 BTU per hour
- Operating Inlet pressure: max. 1/2 PST, Natural gas 7.0" w.c., LP 11.0" W.C.
- Range of Modulation: Natural gas 1.7"-4" w.c. +/-.3" w.c., LP 5"-10" w.c. +/-.5" w.c.
Mechanical Requirement for Gas Control:
[0069] 1/2" or 3/4" Inlet and Outlet
Electrical Requirement
[0070]
- Gas Control: 24 VAC
- Sensor: 5 VDC, Analog output: 0 -4 VDC
- Modulation: 5 VDC
Configuration: Furnace T1. Sampling system T2, Sensor T3
[0071]
- Copper Tubing needs to be short to minimize differential of T1 and T2, dia. of .25"
to .5"
- Copper Tubing in vertical coil to cool the flue down to 140 degreed F. and remove
condensation
- At 1cc/min. flow rate of CO2 sapling from T1, through T2, to T3
Operation Requirement
[0072]
- Preferred range of CO2 concentration for optimum combustion efficiency is about 7.5%
to 8.0%
- If 9% of CO2, outlet gas pressure should be modulated downward from 4.0" to 2.97"
- If 6.5%, outlet gas pressure should be modulated upward from 4.0" to 4.5" w.c.
- If 9.5%, outlet gas pressure should be modulated downward by 1" w.c.
- A .5% change of CO2 would result in a modulation of outlet pressure by .36 - .39" w.c.
Sensor
[0073]
- Power consumption: 150mA peak, 30mA average. Power supply 5VDC +/-5%.
- Range of measuring: 7% to 11%, accuracy +/-5% of reading
- Gravity flow rate of CO2 is 1cc per minute
- Operational temperature is 10 to 185 degrees F., relative humidity 0 to 100%, non-condensing
- Warm Up Time: 20 minutes
- Response Time: TBD as it is up to length of tubing, its area, and flow rate of 1cc/minute
- Step Response Time (to 90% of the step - 5 minutes