GB2511774A - Monitoring the ambient temperature of an incubator - Google Patents

Abstract

In order to generate a warning when the ambient temperature of an incubator 100 strays above or below operational limits, a power input parameter P of the incubators climate controller 130 is determined over a sample time and if the power input parameter is greater than a first threshold or less than a second threshold, an alarm is sounded. This avoids inaccuracies in temperature-measuring methods due to the proximity of other heat sources, such as the eggs or chicks themselves. The climate controller, typically a heater, can be controlled by pulse modulation, in which case the power input parameter can be measured by ascertaining the proportion of the sample time during which the climate controller is on.

Description

MONITORING THE AMBIENT TEMPERATURE OF AN INCUBATOR

The invention relates to temperature-controlled chambers such as incubators, in particular egg incubators.

Incubators artificially provide the egg with the correct controlled environment for the developing chick. Depending on complexity, an incubator will give varying degrees of control over temperature, humidity, egg turning, fresh air flow and hygiene, while providing a secure place for the eggs. Accurate incubation temperature is by far the most important requirement for successful hatching of chicks. Even marginal temperature differences can affect hatch rates. The growth processes in the development of the embryo are very temperature-sensitive and a small deviation can cause development to progress out of sequence, resulting in losses or deformities.

Therefore, the air temperature around eggs in an incubator must remain within a small margin of the ideal, or hatch rates will be greatly reduced. A target incubation temperature can be defined which is dependent on the type of egg to be incubated and the type of incubator used. However, temperature control is obviously important for other kinds of incubator also.

The temperature is maintained by a heater within the incubator, controlled in dependence on a thermostat, likewise in the incubator. A temperature sensor apparatus located among the eggs is shown for instance in WO 2005/013678 (Univ Leuven). Heating and cooling is the concern of US 5025619 (R W Cannon). Cooling is a concern particularly in large incubators and hot countries.

Ideally, the maximum temperature variation inside the incubator chamber is ±0.25°C across the egg tray and ±0.25°C over a period of time. However, this is difficult to achieve in real-life conditions. Egg incubators may be located in outbuildings or barns, which can experience large fluctuations in ambient temperature.

As the ambient room temperature falls, the temperature difference between the air in the incubation chamber and the outside air increases. This causes greater variations in the air temperature around the eggs. This may cause some embryos to die, even though the measured air temperature at the control thermostat remains within normal limits. Moreover, if the ambient room temperature continues to fall, for example at night, at some point the difference between room and incubator temperature will become greater than the incubator heater is capable of offsetting. This results in incubator temperature falling below set point, with serious loss of incubating eggs or other animals in the incubator. Without advance warning it may be difficult for the operator to take suitable remedial action.

As room temperature rises, on the other hand, a point is reached where the heat created by electrical components within the incubator, together with the heat created by the bird embryos or animals, becomes greater than the heat lost from the incubator to the room. This occurs gradually and causes variations in air temperature around the eggs or animals. This also may cause some embryos to die while the measured air temperature at the control thermostat remains within normal limits. The number of live embryos or animals in the incubator creating metabolic heat will vary the room temperature at which this effect happens. It room temperature continues to rise, for example due to direct sunlight, the overall air temperature in the incubator will also rise and result in serious loss of incubating eggs or animals.

An incubator will give best results in a room free from wide temperature variations and with generous ventilation -particularly if several incubators are running at the same time. Ideally the room temperature will be between 20°C and 25°C (68°F and 77°F).

Therefore, it is advantageous to have a warning system that indicates when room temperature is outside of the operational limits for the incubator and its current contents of eggs or animals.

It is known to measure room tempelature using an external thermal sensoi provided on or near the external surface of the incubator. However, such a sensor is subject to errors due to the proximity of other heat sources or objects placed near the sensor that pievent acculate room-temperature measurement. Fuither, a typical alarm system based on fixed uppei or lower air tempelature limits will not take account of heat created by developing embryos or animals and may be prone to false alarms or be insensitive.

The invention aims to overcome or mitigate these problems.

The invention is defined in the attached independent claims, to which reference should now be made. Preferred features may be found in the sub-claims appended thereto.

In embodiments of the invention, the input power for the heating (oi cooling) element, or a quantity oi palameter related to or derived from this input power, is used as an indication of the rate of heat loss to (or uptake from) the room, and therefore can indicate when the room temperature is becoming too high or low for the given number of eggs or animals in the incubator. Calculated or measured input power may be compared with set limits to trigger a warning to the operator befoie embryos, a other organisms, are lost because of under-or over-heating.

This way of generating an indication of ambient temperature is not sensitive to local factors, such as the layout of the incubator, or the location and nature of other objects in the loom.

The input power can be measured or calculated in a simple manner if the heater is controlled by pulses. For instance, if the heater is either on or off over a cycle period, such as 0.5 seconds, the input power is determined by the proportion of that period for which the heater is on, giving a measure of the input power. This proportion can be ascertained eithei directly, e.g. by a sampling method, or by inference from an existing control parameter, such as a PWM parameter.

If this input power as measured is greater or less than a threshold, an alarm is raised.

To prevent accidental outliers, an alarm delay is preferably built in, so that the power, or power parameter, has to be outside the threshold for a minimum time, which may be of the oider of minutes or houis.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figuies 1 to 4 show incubators of various types to which the invention can be applied; and Figure 5 shows an example of a method in accordance with the invention to monitor the ambient temperature of an incubator.

Figure 1 shows a still air incubator 100. The insulated box 110, 112 forms an enclosed chamber 120 with an electric heater 130 in the upper pait and a lid 110 to allow access to the chambei 120. A thermostat oi temperature contioller 172 controls the heater.

Inside the chamber is provided a platfoim for eggs 160, a thermometei 170 and tray for water 150.

Figure 2 shows a forced air incubator 200 with a removable lid 210 base 212 forming an enclosed chambei 220. The tempeiature of the air in the chamber is monitored by a thermometer 270 and the electric heater (not shown) is controlled by the temperature sensor 272. The incubator includes a circulating fan 240 to circulate air around the enclosed chamber 220. An egg tray 260 is provided at the lower part of the chamber and has a water tray 250 underneath it. A wet-bulb thermometer 274 monitors humidity.

The incubator 200 can be provided with means for turning or rotating the eggs, such as tilting trays, trays with a moving floor or trays with rollers.

Figure 3 shows a contact incubator 300 having an enclosed chamber with a lid.

A heater is provided in the form of an inflatable skin 330 which is aftached to the inside of the lid 310. This skin 330 when inflated provides warmth by contact with the tops of the eggs 305, mimicking the functions of an incubating parent. An egg-turning conveyor 360 is provided at the lower part of the chamber 320, which moves to turn the egg when the contact skin 330 is retracted. A cooling fan 340 and humidity control pump 350 are provided and are controlled to regulate the environmental conditions within the chamber 320.

Figure 4 shows a cabinet incubator 400 having a door 412 and an enclosed chamber 420. A heater (not shown) is located in the base (or the rear, or the top) of the cabinet. Inside the enclosed chamber 420 are multiple tiltable egg trays 460 which can be automatically controlled. Fans (not shown) are located at the rear of the chamber 420 and provide improved temperature distribution. A control panel 480 on the front of the cabinet 400 has a digital display and allows the user to adjust parameters and seftings on the incubator, such as internal incubation temperature, internal humidity, ventilation and egg tray position. In the upper part of the chamber 420 is a water tray 450. The cabinet 400 can also be fitted with a controllable humidity pump (not shown) having an external reservoir which maintains the internal humidity irrespective of changes in the room humidity levels.

In any of these types, in order to maintain a suitable temperature in the incubator, the output of the heater is controllable. This can be done by switching it on and off at different times, using time proportional control, using PWM (pulse width modulation), by varying the voltage, or by other suitable means.

An on/off pulse heater can typically have a pulse frequency of between 0.1 Hz and 100kHz, more particularly between 2Hz and 5Hz. Here, the heater has a pulse frequency of 2Hz, which means that there are two pulses per second and that each pulse is up to 0.5 seconds long. Control is carried out by having the heater either on or off for varying times within the individual pulse intervals. The length of time for which the heater is on during each interval is derived from measurement of the temperature within the incubator. The measured temperature is compared to a target temperature, and the output of the heater is varied to achieve a steady temperature inside the incubator.

In this simple embodiment there are just three levels: the pulse width is 0, 50% or 100%.

If the measured temperature is below a lower temperature threshold, for example 0.15 00 below the target temperature, the heater is on for the entire interval. If the measured temperature is greater than an upper temperature threshold, for example 0.05 00 above the target temperature, the heater is off for the entire interval. If the measured temperature is between the upper and lower threshold, the heater is on for half of the interval. This could be described as a rudimentary PWM system, and clearly the grain could be finer.

The invention uses a measure of this power input as a proxy for determining the outside temperature, and hence sounding the alarm if this temperature becomes too high or too low for too long, as will now be explained.

Figure 5 is a flow chart showing a first method of determining the power input to an incubator, which can be of any of the types of incubator above or another type, by determining the time that the heater is operating with respect to total time and comparing this value to predetermined maximum and minimum threshold values. The heater is assumed to be an on/off pulse heater as described above. The method samples the heater output over a certain period (total time), and generates a power input parameter on the basis of the proportion of the samples for which the heater was on.

The power input parameter P is determined and is compared to an upper and lower threshold (PTU, PTL) to trigger low and high room temperature warnings. That is, if the power input parameter is very high, the room is too cold, and vice-versa. A countdown or delay is featured that prevents over-sensitivity to short-term variations (for instance the initial warming of the incubator from cold up to the control temperature, or when a door is opened).

A counter loop is used to determine the heater power in terms of the time the heater is actually on versus total time. A Total Time Counter (TTC) records the total time for a number of samples, and a Heater Time Counter (HTC) records for each sample whether the heater is on. The counter loop time is defined by the time to process each loop and may be varied by altering a Delay built in to the loop. The counter loop frequency should be significantly higher than the heater pulse frequency to ensure that whole pulses are not missed between counts. The Delay can be preset in accordance with the operating parameters of the heater. Alternatively, the Delay can be defined by the user, for example using a control panel on the incubator. For a pulse heater with an operating frequency of 2Hz (as described above), the Delay could be in the range 0.05-0.1 seconds; here the Delay is 0.1 seconds, in which case the on/off state of the heater is checked 10 times per second.

The counter loop continues to check the on/off state of the heater for a defined total time TIdAL The total time TIOTAL is determined when the TTC counter reaches TLIMII, where TL-= total time TIOTAL divided by Delay. For example, if a total time TIOTAL of 10 minutes is required with a Delay of 0.1 seconds, TLIMII is 6000 (a notional value of 100 is shown in Figure 5, to give a percentage).

The total time TIOTAL and/or parameter TLIMIT can be preset in accordance with the operating parameters of the heater. Alternatively, the total time TIOTAL and/or parameter TLIMI-I-can be defined by the user, for example input into a control panel on the incubator.

After the TTC value reaches TLIMIT, the HTC value is compared to a High Room Temperature Alarm Threshold PI-[. If the HTC value is less than this threshold (that is, the heater has not been in operation as much as would be expected in a room at normal ambient temperature), the High Room Temperature Alarm Delay Countdown is started, or allowed to continue, if it is already running. If the HTC value is greater than this threshold, the High Room Temperature Alarm Delay Countdown is reset.

The High Room Temperature Alarm Threshold PIL can be set to any value. Typically the High Room Temperature Alarm Threshold PT[ might be between 0 and 30, as a percentage, say particularly between 5 and 20. In this embodiment, the High Room Temperature Alarm Threshold PIU is 5. This means that if the heater is operating for less than 5% of the total time, the High Room Temperature Alarm Delay Countdown is started. However, the actual value depends on a number of factors, such as the size and layout of the incubator.

The HTC value is then compared to a Low Room Temperature Alarm Threshold P-i-u. If the HTC value is greater than this threshold, the Low Room Temperature Alarm Delay Countdown is started, or allowed to continue. If the HTC value is less than this threshold, the Low Room Temperature Alarm Delay Countdown is reset.

The Low Room Temperature Alarm Threshold P-1-u can be set to any value, though of course it is higher than the High Room Temperature Alarm Threshold P1u. Here, the Low Room Temperature Alarm Threshold P1u is 90. The controller then checks the High Room Temperature Alarm Delay Countdown. If the High Room Temperature Alarm Delay Countdown has elapsed, the High Room Temperature Alarm is indicated or activated. If the High Room Temperature Alarm Delay Countdown has not elapsed, the controller then checks the Low Room Temperature Alarm Delay Countdown. If the Low Room Temperature Alarm Delay Countdown has elapsed, the Low Room Temperature Alarm is indicated or activated.

If the Low Room Temperature Alarm Delay Countdown has not elapsed, the TTC and HTC are reset to 0 and the above steps are repeated from the beginning.

Clearly the steps need not be performed in the order shown in Figure 5-high temperature can be tested in each loop before or after low temperature.

The High Room Temperature Alarm Delay Countdown and Low Room Temperature Alarm Delay Countdown can be set to any value, but should be long enough to eliminate over-sensitivity to short-term variations (for instance the initial warming of the incubator from cold up to the control temperature). The Room Temperature Alarm Delay Countdown can be preset. Alternatively, the Room Temperature Alarm Delay Countdown can be defined by the user, for example input into a control panel on the incubator. Typically the duration of the Room Temperature Alarm Delay Countdown is a matter of hours, e.g. 0.5-5 hours, say about 1 hour.

Such a sampling method is of general application. Instead of sampling the heater input from outside, as it were, it would however be possible to use the output of the PWM controller directly to generate the Power Input Parameter.

The PWM heater controller can typically have a pulse frequency of between 0.1 Hz and kHz, more particularly between 2 kHz and 50 kHz. The microcontroller has a built-in calculator that creates a power output based on the measured temperature and the target temperature. The power output can be any percentage of the maximum power of the heater and the heater can operate for any portion of the pulse. In this case a power input parameter P can be directly calculated using the output data from the PWM microcontroller. The power output is averaged/summed over a total time T-roTA[tO determine the power input parameter P. The alarm indication may take the form of audible or visual warnings. The alarm indication may be latched to continue to show the alarm situation after the event has finished, for instance the room temperature rises again after a cold night or falls after a hot day.

The invention is described with specific reference to egg or animal (or microorganism) incubators, but it could be applied to other apparatus where a temperature in a chamber is to be maintained in varying ambient.

Claims (8)

1. CLAIMS: 1. A method for monitoring the ambient temperature of an incubator (100, 200, 300, 400) having a chamber (120, 220, 320, 420) with a climate controller (130, 230, 330, 430) for maintaining the chamber at a constant temperature, comprising: -determining a power input parameter (P) of the climate controller (130, 230, 330, 430) over a sample time (TTG); and -if the power input parameter (P) is greater than a first threshold (P-i-a) or less than a second threshold (PTL), indicating an alarm.
2. 2. A method according to claim 1, wherein the climate controller (130, 230, 330, 430) is controllable by pulses.
3. 3. A method according to claim 1 or 2, wherein the power input parameter (P) is measured by ascertaining the proportion of the sample time during which the climate controller (130, 230, 330, 430) is on.
4. 4. A method according to claim 1 or 2, wherein the power input parameter (P) is calculated directly from the power output of a PWM microcontroller.
5. 5. A method according to any preceding claim, wherein the first threshold (Piu) is between 0.7 and 1.0 and the second threshold (PIL) is between 0.0 and 0.3.
6. 6. A method according to any preceding claim, wherein the climate controller is a heater.
7. 7. A method according to any preceding claim, wherein the apparatus is an egg incubator.
8. 8. An apparatus (100, 200, 300, 400) having a chamber (120, 220, 320, 420) with a climate controller (130, 230, 330, 430) for maintaining the chamber at a constant temperature, further including an alarm system, the alarm system including a power input determination portion for ascertaining the power of the heater over a given sample time, and an alarm-generating portion for generating an alarm if the power input thus determined) is greater than a first threshold (P-i-u) or less than a second threshold (P-I-L).