JPS63123946A - Space cooling operation controller of multichamber type air conditioner - Google Patents

Abstract

PURPOSE:To operate the title controller with appropriate capacity in correspondence to the change in the number of indoor units to be operated by correcting a compressor operating frequency corresponding to the total sum of the capacity of indoor units, depending upon whether a difference between the estimated value and the target value of a saturation evaporation temperature on the low-pressure side of a coolant circuit after a constant time is within a proper and correct region or not. CONSTITUTION:At the time of starting the space cooling operation and at the time of varying the number of indoor units 21a and 21b operated, a compressor 7 is operated at a frequency corresponding to the total sum of the capacity of indoor units determined by capacity total sum determining means 25 and operational frequency determining means 26. During the operation of the compressor 7, while detecting the saturation evaporation temperature by means of detecting means 27, the saturation evaporation temperature after a fixed time is estimated by means of estimating means 28. The operational frequency of the compressor is corrected for adjustment by a value obtained by multiplying the difference between the estimated value thus obtained and the target value by a gain represented by the function of the total sum of the capacities of operating indoor units,depending upon whether the difference between the estimated value and the predetermined target value is within a proper and correct region or not. Accordingly, the operational frequency control of the compressor 7 at the time of space cooling becomes possible with a short transient time and a high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cooling operation control device for a multi-room air conditioner in which a plurality of indoor units can be connected to a refrigerant circuit to one outdoor unit.

[Conventional technology]

FIG. 10 is a circuit diagram showing a conventional control device for a multi-room air conditioner disclosed in, for example, Japanese Unexamined Patent Publication No. 57-55342. In the figure, 1 is a compressor speed control circuit, and 2 is a three-phase AC power supply. The compressor speed control circuit 1 includes a three-phase full-wave rectifier circuit 3 that converts three-phase alternating current into direct current, a direct current voltage adjustment circuit 4 connected to the output side of this rectifier circuit 3, and a direct current voltage regulator circuit 4 that converts a three-phase alternating current into direct current. The inverter circuit #5 is composed of an inverter circuit 5 made up of power transistors for converting into alternating current, and a compressor 7 is connected to the inverter circuit #5.

6 is a control circuit that controls the voltage of the DC voltage adjustment circuit 4 and the frequency of the inverter circuit 5; 8 is a maximum value selection circuit; 9a
, 9b, 9c are temperature difference signals E ta from a plurality of indoor units,
Input terminals to which Etb and Ete are respectively applied; 10a, 10b, 10c are voltage comparators; 11
a.

11b and Ilc are diodes, 12 is a resistor, and 13 is an output terminal that outputs a voltage Vs.

Next, the operation of the air conditioner control device configured as described above will be explained. Temperature difference (difference between room temperature and set temperature) signal voltage E ta applied to each input terminal 9a, 9b, 9c from a plurality of indoor units.

E tb and E te are the voltage comparator 10a, respectively.
10b.

It is input to the ten input terminal of 10c. Further, one input terminal of each of the voltage comparators 10a, 10b, and 10c is connected to the output terminal 13. Therefore, the reference voltages of these voltage comparisons @5loa, 10b, 10c are all the same value Vs, and this vS is the input E ta, E t
b, E tc is determined by the maximum value, and this maximum value is taken as the output voltage VS. This output voltage vS is input to the control circuit 6, and the control circuit #! By applying a frequency control signal from 6 to the inverter circuit 5 as a function of Vs, the compressor is operated at a frequency corresponding to a value that is larger by the same amount of temperature difference signals of each indoor unit.

[Problem that the invention seeks to solve]

Conventional multi-room air conditioner control devices are configured as described above, so they process temperature difference signals for each indoor unit,
It is expensive because it needs to have a function that can exchange information with the microcomputer of the outdoor unit, and when the number of indoor units in operation changes, for example, when additional indoor units are operated whose temperature difference is less than the maximum temperature difference, compression is required. The ability of the aircraft could not be changed, and there was a problem with the lack of ability.

This invention was made to solve the above-mentioned problems, and is a relatively inexpensive multi-room air conditioner that can constantly operate the compressor at the appropriate capacity and efficiently in response to changes in the number of units in operation. The purpose is to improve the cooling operation control device of the machine.

[Means for solving problems]

The cooling operation control device for a multi-room air conditioner according to the present invention includes a means for determining the number and capacity of the indoor units in operation to determine the total capacity of the indoor units in operation, and a means for determining the total capacity of the indoor units in operation; means for determining the operating frequency of the compressor in accordance with the above, means for detecting the saturated evaporation temperature or low pressure on the low pressure side of the refrigerant circuit, means for predicting the value after a certain period of time from this detected value, and this predicted value. and means for determining whether the difference between the target value and the predetermined target value is within an appropriate range, and means for correcting the compressor operating frequency determined according to the sum of the indoor functional forces based on the determination result. That's what happens.

[For production]

In this invention, at the start of cooling operation and when the number of operating indoor units changes, the compressor is operated at a frequency corresponding to the total indoor functional power determined by the total capacity determining means and the operating frequency determining means, While detecting the saturated evaporation temperature or low pressure during the process, and predicting the saturated evaporation temperature or low pressure after a certain period of time, depending on whether the difference between this predicted value and a predetermined target value is within the appropriate range. The compressor operating frequency is corrected by a value obtained by multiplying the difference between the predicted value and the target value by a gain expressed as a function of the total capacity of the operating indoor units. Therefore, it is possible to control the operating frequency of the compressor during cooling with short transient time and high reliability.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system block diagram of a cooling operation control device for a multi-room air conditioner showing one embodiment of the present invention. In the same figure, the outdoor unit indicated by the overall reference numeral 20 includes a compressor 7,
A four-way valve 14 connected to the discharge side and an outdoor heat exchanger 1
5, an accumulator 16 connected between the suction side of the compressor 7 and the four-way valve 14, an accumulator internal heat exchanger 17 disposed within the accumulator 16 and directly connected to the outdoor heat exchanger 15, and an accumulator internal heat exchanger 17. Vessel 17
Electronic linear expansion valve (hereinafter referred to as L) connected in parallel to the other end
(referred to as EV) 18a, 18b and outdoor heat exchanger 15
and a connection point between the four-way valve 14 and the accumulator 16, and a capillary tube 19 connected between the connection point between the four-way valve 14 and the accumulator 16. 21a and 21b are indoor units, and one end of the indoor heat exchanger 22a and 22b is connected to each LEV 18a and 18b of the outdoor unit 20, and the other end is connected to the four-way valve 14. Further, 23 connects the west valve 14 and the accumulator 1 via a capillary tube 19 from between the outdoor heat exchanger 15 and the accumulator internal heat exchanger 17.
This is a temperature sensor that detects the saturated evaporation temperature from the refrigerant circuit connected between 8 and 8. 24 is each indoor unit 21a.

Operating indoor unit determining means 25 determines which indoor unit is in operation based on the operating command from 21b;
2G is the total sum of functional power in the driver's room ΣQi determined by the determining means 25; A compressor operating frequency determining means determines the compressor operating frequency F''-1 as a function f(ΣQi), and 27 is a saturated evaporation detecting means for detecting and storing the saturated M temperature based on the signal from the saturated evaporating temperature detection temperature sensor 23. , 28 is means for determining a predicted saturated evaporation temperature (hereinafter referred to as ETo), which is the saturated evaporation temperature after a fixed time from the final measurement, based on the saturated evaporation temperature by the detection means 27, and 29 is the ETo predicted by the determination means 28. Control saturated evaporation temperature determining means 30 determines a controlled saturated evaporation temperature (hereinafter referred to as ΔET) obtained from the difference between the target evaporation temperature and a preset target evaporation temperature (hereinafter referred to as ET+n); Temperature (ΔE T = E T o −E
Appropriate control saturated evaporation temperature determination means 31 determines whether or not T rn ) is within a preset appropriate range; 31 indicates the determination result by the determination means 30, that is, when ΔET is outside the appropriate range, the compressor operating frequency The correction value (hereinafter referred to as ΔF) is the ΣQ! determined by means 24 and 25. function G(Σ
ΔF=value obtained by multiplying ΔET by the gain given from Qi)
Compressor operating frequency correction value determining means 32 determines the compressor operating frequency correction value to be ΔF=O when it is in the appropriate range. In addition to Fj-1, which is set as the previous compressor operating frequency when the compressor operating frequency is changed at regular intervals, it is a compressor operating frequency determining means that determines a new compressor operating frequency Fj, and 33 This is a compressor operating frequency control means that controls the operating frequency of the compressor 7 to the compressor operating frequency determined by the frequency setting means 26 or 32.

34 is a compressor operating frequency control device consisting of these means 24-33.

FIG. 2 is a block diagram showing an example in which the compressor operating frequency control device 34 of FIG. 1 is implemented using a microcomputer. In the figure, numeral 39 is a microcomputer (hereinafter referred to as microcomputer), and this microcomputer 39 has a central processing unit (hereinafter referred to as CPU) 45 and a system for causing the CPU 45 to perform the processing of each means 24 to 32 shown in FIG. It is comprised of a memory 46 for storing programs, calculation results from the CPU 45, and other data, an input circuit 49, and an output circuit 48. Above input circuit 4
7, ink faces 40a, 40 for inputting operating signals from the indoor units 21n, 21b and to the microcomputer 39;
b is connected. Further 41a.

41b is an indoor functional power setting circuit for setting the capacity of the indoor units 21a and 21b, each of which has a plurality of switches 42a.

42b and pull-up resistors 43a and 43b. 44 is A that converts the saturated evaporation temperature signal from the temperature sensor 23 into a digital signal and inputs it to the microcomputer 39;
-D converter. In addition, 36a and 36b are the indoor units 21
While transmitting the operation commands of a and 21b to the outdoor unit 20,
The control circuits 37a, 37b, 38a, and 38b (, which control the indoor units) are connectors for operating signal transmission lines that connect the indoor units 21a, 21b and the indoor unit 20.The output circuit 49 includes an inverter. A control circuit 6 is connected, and its control command signal is output to the compressor operation control circuit 1.

The compressor speed control circuit 1 includes a three-phase full-wave rectifier circuit 3 that converts a three-phase AC power source 2 into DC, a smoothing circuit @ 35 that smoothes this DC voltage, and an inverter control circuit 6 that converts the DC voltage.
The inverter circuit 5 is composed of an impark circuit 5 that converts the AC into three-phase AC of an arbitrary frequency according to a command signal from the inverter circuit 5.
The output from the compressor 7 is supplied to the compressor 7.

FIG. 3 is an operating characteristic diagram showing the relationship between the total indoor functional power and the compressor operating frequency. By varying the frequency of the power supply supplied to the compressor 7, that is, the operating frequency, the rotational speed of the compressor can be varied, and the capacity of the compressor can be freely varied. As shown in the figure, for example, when the indoor unit 21a with a small capacity Q is operated independently, the compressor operating frequency is set to the lowest (Q,), and when the indoor unit 21b with a large capacity Q2 is operated independently, t(Q2 ), and then both indoor units 21
When driving both a and 21b, the total indoor functional power is Q.
+ 1Q 2, and the operating frequency is the highest f (Ql
+Q2).

FIG. 4 is an operating characteristic diagram showing the relationship between the controlled saturated evaporation temperature ΔET and the compressor operating frequency, and shows that the higher the compressor operating frequency, the lower the ΔET. Considering the change in the load on the compressor 7 determined by the air temperature and humidity of the indoor and outdoor units as a parameter, when ΔET is positive, the load is large, and when ΔET is negative, the load is small, and it can be said that the load is appropriate in the appropriate range. In the figure, when ΔET is at point A, the saturated evaporation temperature is lower than the target saturated evaporation temperature, and the air conditioner has overcapacity, so the operating frequency of the compressor must be reduced by ΔF to make ΔET appropriate. lower the FA frequency to A8
It is necessary to In addition, when ΔET is at 0 point, the saturated evaporation temperature is higher than the target saturated evaporation temperature, and the air conditioner is insufficiently capable.In order to make ΔET appropriate, the operating frequency of the compressor must be increased by ΔF. , it is necessary to set the frequency of Fo to F8. Therefore, since ΔF is a value determined based on the magnitude of ΔET, when ΔF is expressed as a function of ΔET, it is expressed as ΔF(ΔET)=kXΔET. k
is a proportionality constant (hereinafter referred to as gain).

FIG. 5 is an operating characteristic diagram showing the relationship between the controlled saturated evaporation temperature ΔET and the compressor operating frequency correction value ΔF (ΔET, ΣQi), where the unit controlled saturated evaporation temperature ΔETo.

In other words, the compressor operation number correction value ΔF when the controlled saturated evaporation temperature changes is the total capacity of the operating indoor units ΣQ! This shows that it is a function of That is, when the air conditions of the indoor and outdoor units are constant, the parameter of the compressor load is determined by the total capacity ΣQi of the operating indoor units. The larger the total capacity ΣQi of the operating indoor unit, the greater the ΔE when changing the unit frequency.
Since the change in T becomes small, the controlled saturated evaporation 1 degree ΔETo
In order to greatly change ΣQi, it is necessary to change the compressor operation number more greatly as ΣQi becomes larger. Therefore, the formula for the compressor operating number correction value ΔF above is ΔF(ΔET)−kxΔ
The gain k of ET is expressed as a function of ΣQi, and ΔF is expressed as K=
If G (ΣQi), ΔF (ΔET, ΣQ1) = Δ
It can be expressed as ETXG(ΣQi). In addition, in FIG. 5, in the case of independent operation of the indoor unit 21a,
The compressor operating frequency correction value ΔF is ΔF [ΔF T o ,
Q + ), in the case of independent operation of the indoor unit 21b, ΔF is Δ
F(ΔETO-Q2) - In the case of simultaneous operation of indoor units 21a and 21b, ΔF is ΔF(ΔF T I , Q ,
2), and if ΔET0 is positive, the magnitude relationship is
ΔF(ΔETo, Ql +Q2)〉ΔF(ΔF To
, Q2 )>ΔF(ΔET0°Q,). on the other hand,
If ΔET0 is negative, ΔF(ΔET0.Q+)>ΔF
(ΔETo, Q2)〉ΔF(ΔETO, Ql +Q2
).

Next, the operation of the cooling operation control device of this embodiment configured as described above will be explained based on flowchart 1 in FIG.

The indoor unit 21a is set to Nal, and the indoor unit 21b is set to M2.

When the program starts to control the cooling operation of the air conditioner, it is determined in step 49 whether No. 1 is in operation, and if "NO", it is determined in step 50 whether Ion 2 is in operation. Also, in step 49, rY E
If SJ, the process moves to step 51 and it is determined whether Isao 2 is driving. &1. If No. 2 is in operation, step 52; if only No. 1 is in operation, step 5
In step 54, when only Na2 is in operation, the frequency data corresponding to the predetermined capacity sum ΣQi is assigned to F''-1, and at the same time, Mo, l, No.
, 2 are both in operation, set "3" in step 55, and set Nl1 to "3" in step 55.
If only 1 is in operation, enter "1" in step 56, No, 2.
In the case of only operation, in step 57, [2J is each substituted into Nj-1 as old mode operation data. As a result, in step 58, the compressor 7 starts operating based on the old frequency data Fj-1. On the other hand, N11.1. If both &2 are not in operation, the process moves to step 59, and the compressor 7
The operation of the system continues to be stopped. Next, when the compressor 7 starts operating in step 58, a timer T for frequency control is set in step 60, the saturated evaporation temperature ET is measured by the temperature sensor 23 in step 61, and the saturated evaporation temperature ET is measured in step 61.
2, this ET is stored in the memory 46 of the microcomputer 39. Then, in step 63, it is checked whether the timer T has reached the frequency control time t. When the timer T reaches, the process proceeds to step 64, and based on the ET data previously stored in the memory 46 and the latest ET data,
The ET after t2 hours from the current time ('r=t + ) is predicted, and the predicted saturated evaporation temperature ETo is determined. Next, in step 65, the target saturated evaporation temperature ETm is set in advance.
is subtracted from ETo obtained in step 64 to obtain the controlled saturated evaporation temperature ΔET. Then, in step 66, it is determined whether or not ΔET is within the appropriate range. If it is not within the appropriate range, in step 67, ΔET obtained in step 65 is multiplied by a preset gain G (ΣQi) to perform compression. Find the machine operating frequency correction value ΔF. In the next step 69, data obtained by adding ΔF to the frequency data Fj-1 is substituted into the new frequency data Fj. On the other hand, if it is within the appropriate range, rQJ is substituted for ΔF in step 68 and the process moves to step 69. Using the new frequency data obtained in this manner, the inverter circuit 5 is controlled in step 70 to change the operating frequency of the compressor 7. Thereafter, in step 71, a frequency control timer T is set. Then, in the next step 72, 73, and 74, check the operating indoor unit, and if No. 1, No. 2 are operating together, enter "3" in step 75; if only No. 1 is operating, enter "3" in step 7.
Step 77 if you are driving only No. 6 and No. 2.
Then, r24 is assigned to N'' as new mode operation data.

Further, in step 63, the timer T sets the frequency control time t,
If it has not yet reached step 72, the process jumps to step 72 and executes steps 72 to 77. If Nj and Nj-1 are equal in step 78, it is assumed that the number of operating vehicles has not changed and the process moves to step 79. If the timer T has been reset in step 79, the new frequency data is replaced with the old frequency data in step 80. Frequency data F j
-1 and return to step 60. Further, if the timer T has not been reset in step 79, the process returns to step 61. Furthermore, in step 78, Nj and N j−1
If they are not equal, it is assumed that there has been a change in the operating indoor unit, and the program returns to step 49, which is the first step in the program.

FIG. 7 shows E of the saturated evaporation temperature in the above-mentioned control tB operation.
This is a timer chart 1 showing changes in T and changes in compressor operating frequency. In the same figure, if the timer T becomes T = t at point A, then the predicted saturated evaporation temperature ETo at point A' after t2 hours have elapsed from point A from ET measured at time t (0→A). When predicted, it becomes EToA, and since this value deviates higher than the appropriate range, the control saturated evaporation temperature ΔET is calculated as ΔETA = ETOA − ETm
(target saturated evaporation temperature), and the correction value ΔFA of the compressor operating frequency correction value ΔF at point A is also ΔFA=ΔET.
AxG (ΣQi) is positive, and at point A, the compressor operating frequency is increased by ΔFA. In this way, the change in ET at the next time t, (A+B) will be larger than the time t, (0-+A), so the change in ET at the next time t, (0-+A) will be greater than the time t, (0-+A).
A) faster than operating at frequency A) (approaching ETm1)
Next, find EToe at point B in the same way as at point A.
EToe deviates to a direction lower than the appropriate range, and ΔET8 becomes negative as ΔET8=ET oB ET m, and ΔET8 becomes negative.
F8 is the negative of ΔF8−ΔET8×G(ΣQi), and Δ
The compressor operating frequency will be lowered by F8. In this way, the ET change at t, (B-hC) is 1 time t.

(A - B) becomes smaller.

At point B, although the actual ET is higher than the appropriate range, the operating frequency of the compressor becomes low, but since the absolute value of ΔFA is greater than the absolute value of ΔFo, the time t+
At a time j at a position higher than the operating frequency of (04A),
(B-e-C) operation is performed.

As a result, if you continue to operate at the operating frequency for time t+ (A=B), it will eventually deviate from the appropriate range, but
By lowering the frequency at point B, the EToc at point C' also falls into the appropriate range, and ET becomes stable near ETm (appropriate range).

FIG. 8 shows another embodiment of the cooling operation control device for a multi-room air conditioner according to the present invention. This embodiment differs from the embodiment shown in FIG. 1 above in that low pressure is detected and the same control as above is performed based on this low pressure. In FIG. 8, the same reference numerals as in FIG. 1 indicate the same or equivalent parts, 81 is a low pressure sensor that detects the pressure on the low pressure side of the compressor, 82 is low pressure pressure detection means, 83 is predicted low pressure determination means, 84 is a control low pressure determining means, and 85 is an appropriate control low pressure determining means. Although the parameter for each of these means 82 to 85 is low pressure, the processing procedure is the same as that for the saturated evaporation temperature, so a description thereof will be omitted.

Figure 9 shows a Mollier diagram. In a general refrigeration cycle shown by the dotted line, in the region It is constant and changes depending on the operating frequency of the compressor 7. Therefore, even if the low pressure (Ps) corresponding to ET is detected from a pressure sensor instead of ET and the operating frequency of the compressor is corrected so that the predicted low pressure falls within the appropriate range, the above embodiment will not work. You can get exactly the same effect.

〔Effect of the invention〕

As described above, according to the present invention, during cooling operation, the pressure wI
The operating frequency of the compressor is determined according to the capacity saturation of the compressor, and this operating frequency is adjusted indoors depending on whether the difference between the predicted value and target value of the saturated evaporation temperature or low pressure during operation is within the appropriate range. The compressor operating frequency can be determined using a correction value for the compressor operating frequency that takes into account the total functional capacity.
With a relatively inexpensive configuration, the control time for the refrigeration cycle to reach a stable system can be shortened depending on the number of operating indoor units.
A highly reliable cooling operation control device for a multi-room air conditioner capable of optimum high-efficiency operation is obtained.

[Brief explanation of the drawing]

Fig. 1 is a system block diagram showing an embodiment of the cooling operation control device for a multi-room air conditioner according to the present invention, and Fig. 2 is a system block diagram showing an embodiment of the system shown in Fig. 1 using a microcomputer. FIG. 3, FIG. 4, and FIG. 5 are respectively operation explanatory diagrams, FIG. 6 is a flowchart showing the operation of this embodiment, and FIG. 7 is a control operation of this embodiment. Figure 8 is a system block diagram showing another embodiment of the present invention, Figure 9 is a Mollier diagram for explaining its operation, and Figure 10 is a conventional multi-room air conditioner. It is a block diagram showing a control device of. 1-Compressor speed control circuit, 2... AC Ts source, 6...
・Inverter control circuit, 7...Compressor, 20...Outdoor unit, 21a, 21b Indoor unit, 2:11-Temperature sensor, 24...Operation indoor unit determination means, 25...Luck@Indoor functional power total determination Means, 26... Compressor operating frequency determination means, 27... Saturated evaporation temperature detection means, 28... Predicted saturated evaporation temperature determination means, 29. Controlled saturated evaporation temperature determination means,
30... Appropriate control saturated evaporation temperature determining means, 31... Compressor operating frequency correction value determining means, 32... Compressor operating frequency determining means, 34... Compressor operating frequency control device, 8
1 - Low pressure pressure sensor, 82... Low pressure pressure detection means, 83... Predicted low pressure pressure determination means, 84... Control low pressure pressure determination means, 85... Appropriate control low pressure pressure determination means. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Fig. 2 Fig. 3 Visit 1 habit ΣQi-→ Fig. 4 Control saturation N brother temperature I Fig. 5 Fig. 9

Claims (4)

[Claims] (1) In a cooling operation control device for a multi-room air conditioner that allows multiple indoor units to be connected to one outdoor unit including a compressor whose speed is controlled by a variable frequency device, the operating indoor unit means for determining, means for determining the total capacity of the operating indoor units from the determination result by this means, means for determining the operating frequency of the compressor in accordance with the total capacity of the operating indoor units determined by this means; means for detecting the saturated evaporation temperature or low pressure on the low pressure side of the outdoor unit refrigerant circuit; means for determining a predicted value after a certain period of time based on the detected value detected by this means; means for determining the control value determined by the target value, means for determining whether the control value determined by this means is within an appropriate range, and means for determining the control value determined by the compressor operating frequency determination means according to the determination result of this means. means for determining a correction value for correcting the compressor operating frequency determined by this means; means for determining a compressor operating frequency in consideration of the correction value determined by this means; A cooling operation control device for a multi-room air conditioner, characterized by comprising means for controlling frequency. (2) The control value determining means determines the control value based on the difference between the predicted saturated evaporation temperature after a certain period of time obtained based on the saturated evaporation temperature obtained from the detection means and a predetermined target saturated evaporation temperature. A cooling operation control device for a multi-room air conditioner according to claim 1, wherein the cooling operation control device is adapted to determine the evaporation temperature. (3) The control value determining means calculates a predicted low pressure after a certain period of time obtained based on the low pressure obtained from the detection means;
2. The cooling operation control device for a multi-room air conditioner according to claim 1, wherein the control low pressure is determined based on a difference from a predetermined target low pressure. (4) The correction value of the compressor operating frequency is set to 0 when the control value is within the appropriate range, and is set to the control value when the control value is outside the appropriate range. The cooling operation control device for a multi-room air conditioner according to claim 1, wherein the correction value is determined by multiplying the correction value by a gain given as a function.