On Jun 23, 9:41�am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote:> Hi Rune, > > > > > > > > >On Jun 22, 4:38=A0pm, Glen Walpert <g...@null.void> wrote: > >> On Wed, 22 Jun 2011 01:28:58 -0700, Rune Allnor wrote: > >> > For those who have too much time on their hands - consider a set-up > lik= > >e > >> > this (view with fixed-width font): > > >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Thermostate =A0 Dim =A0 =A0 =A0 =A0 > =A0= > > =A0 Reservoir > >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0switch > >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0+----+ =A0 =A0+-----+ =A0 =A0 > = > >=A0 =A0 : =A0 =A0 =A0 : > >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0| =A0 =A0| =A0 =A0 > |---= > >----------z =A0 : > >> > Power supply =3D=3D=3D=3D=3D=3D| =A0 =A0|=3D=3D=3D=3D| =A0 =A0 | =A0 > = > >=A0 =A0 =A0 : =A0 z =A0 : > >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0| =A0 =A0| =A0 =A0 > |---= > >----------z =A0 : > >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0+----+ =A0 =A0+-----+ =A0 > +-----= > >--o =A0 o--------- T probe > >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |________________| =A0 =A0 > = > >......... > > >> > We have a heater (the vertically stacked Z's) in a reservoir. The > heate= > >r > >> > is controlled by an on/off thermostate, with tight hysteresis > settings. > >> > The thermo sensor of the thermostate monitors the temperature in the > >> > reservoir. The output of the thermostate is dimmed by a dim switch, > >> > where the setting is known but not the actual factor for power > >> > reduction. > > >> > None of the parameters associated with the power supply / thermostate > / > >> > dim switch / heater are known or logged. > > >> > The one log one has, is a thermo probe independent of everything > else, > >> > that samples and stores the temperature in the reservoir at a rate of > 4 > >> > samples per minute. > > >> > Q: How does one get an estimate of power consumption > >> > =A0 =A0trends in the heater, from this set-up? > > >> > Rune > > >> If your thermostat cycle times (both on and off) are long compared to > >> your sample rate and dim switch output is constant, then rising temp > ~=3D > >> heater on (with some unknown but unimportant delay) and falling temp > ~=3D > >> heater off; power consumption roughly proportional to percentage on > >> time. =A0If dim switch output can vary then possibly measure off time > >> duration only, power roughly proportional to inverse of off time, or > >> factor in rate of temperature rise during heater on time, probably > adding > >> average cooling rate during off time, which presumably continues while > >> heater is on, reducing the apparent heat input bellow actual heat input > >> during on time. =A0If thermostat setting and/or dead band is adjustable > y= > >ou > >> should be able to detect that also with your single sensor and factor > >> them in also. > > >More or less correct. > > >What I did was: > > >- Detect thermostat cycles from T readings > >- Count the number of rise points and fall points within > > �each cycle, to get thermostat on percentage > >- Count the number of measurements per thermostate cycle > >- Multiply the two to get average energy contribution / cycle > > >This works well enough when dim switch and thermostate > >settings are left alone for the duration of the measurement. > > >Rune > > You have been purposefully misleading. You originally said the hysteresis > band was tight, and no further information was known. Your solution is > specifically based on knowing that the hysteresis band is fairly wide, such > that a slow 4 samples per minute log can track the thermostat cutting in > and out, and get a rough estimation of its on off ratio.Sorry, no. The thermostate is governed by the on/off temperature limits, and the distance between these is narrow ('tight'). The distance in time between on/off points follows from the temperature settings and other thermodynamic properties of the system, and can not be controlled by users. I deliberately used the somewhat fuzzy term 'tight' to describe the hysteresis settings, for two reasons: 1) The exact limits are not known (the temperature band is a lot narrower, 0.2-0.5 C, than the precision to which the setpoint is known, +/- 5C ) 2) The time scale between on/off switches (minutes) is orders of magnitude faster than any other varying features in the system (hours) Rune
Puzzle: How to extract desired info from data?
Started by ●June 22, 2011
Reply by ●June 23, 20112011-06-23
Reply by ●June 23, 20112011-06-23
>On Jun 23, 9:41=A0am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: >> Hi Rune, >> >> >> >> >> >> >> >> >On Jun 22, 4:38=3DA0pm, Glen Walpert <g...@null.void> wrote: >> >> On Wed, 22 Jun 2011 01:28:58 -0700, Rune Allnor wrote: >> >> > For those who have too much time on their hands - consider aset-up>> lik=3D >> >e >> >> > this (view with fixed-width font): >> >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 Thermostate =3DA0Di=>m =3DA0 =3DA0 =3DA0 =3DA0 >> =3DA0=3D >> > =3DA0 Reservoir >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0=>=3DA0 =3DA0 =3DA0 =3DA0switch >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0+----+=>=3DA0 =3DA0+-----+ =3DA0 =3DA0 >> =3D >> >=3DA0 =3DA0 : =3DA0 =3DA0 =3DA0 : >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0| =3DA0=>=3DA0| =3DA0 =3DA0| =3DA0 =3DA0 >> |---=3D >> >----------z =3DA0 : >> >> > Power supply =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D| =3DA0=3DA0|=3D3D=3D3D=>=3D3D=3D3D| =3DA0 =3DA0 | =3DA0 >> =3D >> >=3DA0 =3DA0 =3DA0 : =3DA0 z =3DA0 : >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0| =3DA0=>=3DA0| =3DA0 =3DA0| =3DA0 =3DA0 >> |---=3D >> >----------z =3DA0 : >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0+----+=>=3DA0 =3DA0+-----+ =3DA0 >> +-----=3D >> >--o =3DA0 o--------- T probe >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0|_=>_______________| =3DA0 =3DA0 >> =3D >> >......... >> >> >> > We have a heater (the vertically stacked Z's) in a reservoir. The >> heate=3D >> >r >> >> > is controlled by an on/off thermostate, with tight hysteresis >> settings. >> >> > The thermo sensor of the thermostate monitors the temperature inthe>> >> > reservoir. The output of the thermostate is dimmed by a dimswitch,>> >> > where the setting is known but not the actual factor for power >> >> > reduction. >> >> >> > None of the parameters associated with the power supply /thermostat=>e >> / >> >> > dim switch / heater are known or logged. >> >> >> > The one log one has, is a thermo probe independent of everything >> else, >> >> > that samples and stores the temperature in the reservoir at a rateo=>f >> 4 >> >> > samples per minute. >> >> >> > Q: How does one get an estimate of power consumption >> >> > =3DA0 =3DA0trends in the heater, from this set-up? >> >> >> > Rune >> >> >> If your thermostat cycle times (both on and off) are long comparedto>> >> your sample rate and dim switch output is constant, then rising temp >> ~=3D3D >> >> heater on (with some unknown but unimportant delay) and falling temp >> ~=3D3D >> >> heater off; power consumption roughly proportional to percentage on >> >> time. =3DA0If dim switch output can vary then possibly measure offtim=>e >> >> duration only, power roughly proportional to inverse of off time, or >> >> factor in rate of temperature rise during heater on time, probably >> adding >> >> average cooling rate during off time, which presumably continueswhile>> >> heater is on, reducing the apparent heat input bellow actual heatinpu=>t >> >> during on time. =3DA0If thermostat setting and/or dead band isadjusta=>ble >> y=3D >> >ou >> >> should be able to detect that also with your single sensor andfactor>> >> them in also. >> >> >More or less correct. >> >> >What I did was: >> >> >- Detect thermostat cycles from T readings >> >- Count the number of rise points and fall points within >> > =A0each cycle, to get thermostat on percentage >> >- Count the number of measurements per thermostate cycle >> >- Multiply the two to get average energy contribution / cycle >> >> >This works well enough when dim switch and thermostate >> >settings are left alone for the duration of the measurement. >> >> >Rune >> >> You have been purposefully misleading. You originally said thehysteresis>> band was tight, and no further information was known. Your solution is >> specifically based on knowing that the hysteresis band is fairly wide,su=>ch >> that a slow 4 samples per minute log can track the thermostat cuttingin>> and out, and get a rough estimation of its on off ratio. > >Sorry, no. The thermostate is governed by the on/off temperature >limits, and the distance between these is narrow ('tight'). >The distance in time between on/off points follows from the >temperature settings and other thermodynamic properties of the >system, and can not be controlled by users. > >I deliberately used the somewhat fuzzy term 'tight' to describe >the hysteresis settings, for two reasons: > >1) The exact limits are not known (the temperature band is > a lot narrower, 0.2-0.5 C, than the precision to which the > setpoint is known, +/- 5C ) > >2) The time scale between on/off switches (minutes) is orders > of magnitude faster than any other varying features in the > system (hours)That much additional information makes a feasible solution obvious. Without it your solution was amongst the "well if X holds" possibilities. You went beyond merely failing to provide this information, though. You specifically said nothing else was known, which means a solution would have to assume rather open ended timing behaviour. Steve
Reply by ●June 23, 20112011-06-23
On Jun 23, 10:36�am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote:> >On Jun 23, 9:41=A0am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: > >> Hi Rune, > > >> >On Jun 22, 4:38=3DA0pm, Glen Walpert <g...@null.void> wrote: > >> >> On Wed, 22 Jun 2011 01:28:58 -0700, Rune Allnor wrote: > >> >> > For those who have too much time on their hands - consider a > set-up > >> lik=3D > >> >e > >> >> > this (view with fixed-width font): > > >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 Thermostate =3DA0 > Di= > >m =3DA0 =3DA0 =3DA0 =3DA0 > >> =3DA0=3D > >> > =3DA0 Reservoir > >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 > = > >=3DA0 =3DA0 =3DA0 =3DA0switch > >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0+----+ > = > >=3DA0 =3DA0+-----+ =3DA0 =3DA0 > >> =3D > >> >=3DA0 =3DA0 : =3DA0 =3DA0 =3DA0 : > >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0| =3DA0 > = > >=3DA0| =3DA0 =3DA0| =3DA0 =3DA0 > >> |---=3D > >> >----------z =3DA0 : > >> >> > Power supply =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D| =3DA0 > =3DA0|=3D3D=3D3D= > >=3D3D=3D3D| =3DA0 =3DA0 | =3DA0 > >> =3D > >> >=3DA0 =3DA0 =3DA0 : =3DA0 z =3DA0 : > >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0| =3DA0 > = > >=3DA0| =3DA0 =3DA0| =3DA0 =3DA0 > >> |---=3D > >> >----------z =3DA0 : > >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0+----+ > = > >=3DA0 =3DA0+-----+ =3DA0 > >> +-----=3D > >> >--o =3DA0 o--------- T probe > >> >> > =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 > |_= > >_______________| =3DA0 =3DA0 > >> =3D > >> >......... > > >> >> > We have a heater (the vertically stacked Z's) in a reservoir. The > >> heate=3D > >> >r > >> >> > is controlled by an on/off thermostate, with tight hysteresis > >> settings. > >> >> > The thermo sensor of the thermostate monitors the temperature in > the > >> >> > reservoir. The output of the thermostate is dimmed by a dim > switch, > >> >> > where the setting is known but not the actual factor for power > >> >> > reduction. > > >> >> > None of the parameters associated with the power supply / > thermostat= > >e > >> / > >> >> > dim switch / heater are known or logged. > > >> >> > The one log one has, is a thermo probe independent of everything > >> else, > >> >> > that samples and stores the temperature in the reservoir at a rate > o= > >f > >> 4 > >> >> > samples per minute. > > >> >> > Q: How does one get an estimate of power consumption > >> >> > =3DA0 =3DA0trends in the heater, from this set-up? > > >> >> > Rune > > >> >> If your thermostat cycle times (both on and off) are long compared > to > >> >> your sample rate and dim switch output is constant, then rising temp > >> ~=3D3D > >> >> heater on (with some unknown but unimportant delay) and falling temp > >> ~=3D3D > >> >> heater off; power consumption roughly proportional to percentage on > >> >> time. =3DA0If dim switch output can vary then possibly measure off > tim= > >e > >> >> duration only, power roughly proportional to inverse of off time, or > >> >> factor in rate of temperature rise during heater on time, probably > >> adding > >> >> average cooling rate during off time, which presumably continues > while > >> >> heater is on, reducing the apparent heat input bellow actual heat > inpu= > >t > >> >> during on time. =3DA0If thermostat setting and/or dead band is > adjusta= > >ble > >> y=3D > >> >ou > >> >> should be able to detect that also with your single sensor and > factor > >> >> them in also. > > >> >More or less correct. > > >> >What I did was: > > >> >- Detect thermostat cycles from T readings > >> >- Count the number of rise points and fall points within > >> > =A0each cycle, to get thermostat on percentage > >> >- Count the number of measurements per thermostate cycle > >> >- Multiply the two to get average energy contribution / cycle > > >> >This works well enough when dim switch and thermostate > >> >settings are left alone for the duration of the measurement. > > >> >Rune > > >> You have been purposefully misleading. You originally said the > hysteresis > >> band was tight, and no further information was known. Your solution is > >> specifically based on knowing that the hysteresis band is fairly wide, > su= > >ch > >> that a slow 4 samples per minute log can track the thermostat cutting > in > >> and out, and get a rough estimation of its on off ratio. > > >Sorry, no. The thermostate is governed by the on/off temperature > >limits, and the distance between these is narrow ('tight'). > >The distance in time between on/off points follows from the > >temperature settings and other thermodynamic properties of the > >system, and can not be controlled by users. > > >I deliberately used the somewhat fuzzy term 'tight' to describe > >the hysteresis settings, for two reasons: > > >1) The exact limits are not known (the temperature band is > > � a lot narrower, 0.2-0.5 C, than the precision to which the > > � setpoint is known, +/- 5C ) > > >2) The time scale between on/off switches (minutes) is orders > > � of magnitude faster than any other varying features in the > > � system (hours) > > That much additional information makes a feasible solution obvious. Without > it your solution was amongst the "well if X holds" possibilities. You went > beyond merely failing to provide this information, though. You specifically > said nothing else was known, which means a solution would have to assume > rather open ended timing behaviour.As always, once the problem is stated correctly, the solution might be obvious. If you need additional constraints or assumptions, state them and see how that affects what solutions are feasible. As somebody once said "if you can't solve the stated problem, transform it to something you *can* solve." Rune
Reply by ●June 23, 20112011-06-23
On Jun 23, 1:27�am, Rune Allnor <all...@tele.ntnu.no> wrote:> On Jun 22, 4:38�pm, Glen Walpert <g...@null.void> wrote: > > > > > > > > > > > On Wed, 22 Jun 2011 01:28:58 -0700, Rune Allnor wrote: > > > For those who have too much time on their hands - consider a set-up like > > > this (view with fixed-width font): > > > > � � � � � � � � Thermostate � Dim � � � � � � Reservoir > > > � � � � � � � � � � � � � � �switch > > > � � � � � � � � � �+----+ � �+-----+ � � � � : � � � : > > > � � � � � � � � � �| � �| � �| � � |-------------z � : > > > Power supply ======| � �|====| � � | � � � � : � z � : > > > � � � � � � � � � �| � �| � �| � � |-------------z � : > > > � � � � � � � � � �+----+ � �+-----+ � +-------o � o--------- T probe > > > � � � � � � � � � � � |________________| � � ......... > > > > We have a heater (the vertically stacked Z's) in a reservoir. The heater > > > is controlled by an on/off thermostate, with tight hysteresis settings. > > > The thermo sensor of the thermostate monitors the temperature in the > > > reservoir. The output of the thermostate is dimmed by a dim switch, > > > where the setting is known but not the actual factor for power > > > reduction. > > > > None of the parameters associated with the power supply / thermostate / > > > dim switch / heater are known or logged. > > > > The one log one has, is a thermo probe independent of everything else, > > > that samples and stores the temperature in the reservoir at a rate of 4 > > > samples per minute. > > > > Q: How does one get an estimate of power consumption > > > � �trends in the heater, from this set-up? > > > > Rune > > > If your thermostat cycle times (both on and off) are long compared to > > your sample rate and dim switch output is constant, then rising temp ~= > > heater on (with some unknown but unimportant delay) and falling temp ~= > > heater off; power consumption roughly proportional to percentage on > > time. �If dim switch output can vary then possibly measure off time > > duration only, power roughly proportional to inverse of off time, or > > factor in rate of temperature rise during heater on time, probably adding > > average cooling rate during off time, which presumably continues while > > heater is on, reducing the apparent heat input bellow actual heat input > > during on time. �If thermostat setting and/or dead band is adjustable you > > should be able to detect that also with your single sensor and factor > > them in also. > > More or less correct. > > What I did was: > > - Detect thermostat cycles from T readings > - Count the number of rise points and fall points within > � each cycle, to get thermostat on percentage > - Count the number of measurements per thermostate cycle > - Multiply the two to get average energy contribution / cycle > > This works well enough when dim switch and thermostate > settings are left alone for the duration of the measurement.You know neither how much power is delivered when the heater is on nor how much is lost to ambient when the power is off. You know nothing about additions or removals from the vat. How do you calculate energy (which is what I thout you asked) or power (which is what you seem to want)? What have I missed? Jerry -- Engineering is the art of making what you want from things you can get.
Reply by ●June 24, 20112011-06-24
On Jun 23, 4:36�pm, Jerry Avins <j...@ieee.org> wrote:> On Jun 23, 1:27�am, Rune Allnor <all...@tele.ntnu.no> wrote: > > > > > > > On Jun 22, 4:38�pm, Glen Walpert <g...@null.void> wrote: > > > > On Wed, 22 Jun 2011 01:28:58 -0700, Rune Allnor wrote: > > > > For those who have too much time on their hands - consider a set-up like > > > > this (view with fixed-width font): > > > > > � � � � � � � � Thermostate � Dim � � � � � � Reservoir > > > > � � � � � � � � � � � � � � �switch > > > > � � � � � � � � � �+----+ � �+-----+ � � � � : � � � : > > > > � � � � � � � � � �| � �| � �| � � |-------------z � : > > > > Power supply ======| � �|====| � � | � � � � : � z � : > > > > � � � � � � � � � �| � �| � �| � � |-------------z � : > > > > � � � � � � � � � �+----+ � �+-----+ � +-------o � o--------- T probe > > > > � � � � � � � � � � � |________________| � � ......... > > > > > We have a heater (the vertically stacked Z's) in a reservoir. The heater > > > > is controlled by an on/off thermostate, with tight hysteresis settings. > > > > The thermo sensor of the thermostate monitors the temperature in the > > > > reservoir. The output of the thermostate is dimmed by a dim switch, > > > > where the setting is known but not the actual factor for power > > > > reduction. > > > > > None of the parameters associated with the power supply / thermostate / > > > > dim switch / heater are known or logged. > > > > > The one log one has, is a thermo probe independent of everything else, > > > > that samples and stores the temperature in the reservoir at a rate of 4 > > > > samples per minute. > > > > > Q: How does one get an estimate of power consumption > > > > � �trends in the heater, from this set-up? > > > > > Rune > > > > If your thermostat cycle times (both on and off) are long compared to > > > your sample rate and dim switch output is constant, then rising temp ~= > > > heater on (with some unknown but unimportant delay) and falling temp ~= > > > heater off; power consumption roughly proportional to percentage on > > > time. �If dim switch output can vary then possibly measure off time > > > duration only, power roughly proportional to inverse of off time, or > > > factor in rate of temperature rise during heater on time, probably adding > > > average cooling rate during off time, which presumably continues while > > > heater is on, reducing the apparent heat input bellow actual heat input > > > during on time. �If thermostat setting and/or dead band is adjustable you > > > should be able to detect that also with your single sensor and factor > > > them in also. > > > More or less correct. > > > What I did was: > > > - Detect thermostat cycles from T readings > > - Count the number of rise points and fall points within > > � each cycle, to get thermostat on percentage > > - Count the number of measurements per thermostate cycle > > - Multiply the two to get average energy contribution / cycle > > > This works well enough when dim switch and thermostate > > settings are left alone for the duration of the measurement. > > You know neither how much power is delivered when the heater is on nor > how much is lost to ambient when the power is off. You know nothing > about additions or removals from the vat. How do you calculate energy > (which is what I thout you asked) or power (which is what you seem to > want)? What have I missed?You missed the word 'trend' in the problem statement. I can't get the numbers from these kinds of estimates, but you *can* get a rough idea about at what times the heater does hard work, and when it relaxes. Which is just enough to correlate with measurements of other external factors one might suspect influences the system. Rune
Reply by ●June 24, 20112011-06-24
Rune Allnor wrote:> You missed the word 'trend' in the problem statement. I can't > get the numbers from these kinds of estimates, but you *can* > get a rough idea about at what times the heater does hard work, > and when it relaxes. >Your question should have been Q: How does one avoid getting an estimate of power consumption trends in the heater, from this set-up? A: don't look at the data
Reply by ●June 24, 20112011-06-24
On Jun 24, 1:28�am, Rune Allnor <all...@tele.ntnu.no> wrote:> On Jun 23, 4:36�pm, Jerry Avins <j...@ieee.org> wrote: >...> > You know neither how much power is delivered when the heater is on nor > > how much is lost to ambient when the power is off. You know nothing > > about additions or removals from the vat. How do you calculate energy > > (which is what I thout you asked) or power (which is what you seem to > > want)? What have I missed? > > You missed the word 'trend' in the problem statement. I can't > get the numbers from these kinds of estimates, but you *can* > get a rough idea about at what times the heater does hard work, > and when it relaxes. > > Which is just enough to correlate with measurements of other > external factors one might suspect influences the system.Because of the "dimmer", you can't know how hard the heater works. How does knowledge of the heater's duty cycle imply its power? The system needs calibration. Jerry -- Engineering is the art of making what you want from things you can get.
Reply by ●June 25, 20112011-06-25
Jerry Avins wrote:> > On Jun 24, 1:28 am, Rune Allnor <all...@tele.ntnu.no> wrote: > > On Jun 23, 4:36 pm, Jerry Avins <j...@ieee.org> wrote: > > > > ... > > > > You know neither how much power is delivered when the heater is on nor > > > how much is lost to ambient when the power is off. You know nothing > > > about additions or removals from the vat. How do you calculate energy > > > (which is what I thout you asked) or power (which is what you seem to > > > want)? What have I missed? > > > > You missed the word 'trend' in the problem statement. I can't > > get the numbers from these kinds of estimates, but you *can* > > get a rough idea about at what times the heater does hard work, > > and when it relaxes. > > > > Which is just enough to correlate with measurements of other > > external factors one might suspect influences the system. > > Because of the "dimmer", you can't know how hard the heater works. How > does knowledge of the heater's duty cycle imply its power? The system > needs calibration.Suppose this is a hot water heater and suppose he was trying to determine at what times of day hot water is used the most and when it is used least. Or suppose he wants to know if taking a shower in the morning uses more hot water than doing laundry in the afternoon. I don't have any idea why there would be a dimmer in the circuit. -jim> > Jerry > -- > Engineering is the art of making what you want from things you can > get.
Reply by ●June 25, 20112011-06-25
On Jun 25, 7:03�am, jim <"sjedgingN0Sp"@m@mwt,net> wrote:> Jerry Avins wrote:...> > Because of the "dimmer", you can't know how hard the heater works. How > > does knowledge of the heater's duty cycle imply its power? The system > > needs calibration. > > Suppose this is a hot water heater and suppose he was trying to > determine at what times of day hot water is used the most and when it is > used least. Or suppose he wants to know if taking a shower in the > morning �uses more hot water than doing laundry in the afternoon. > > I don't have any idea why there would be a dimmer in the circuit.Unless I misread, he writes that he wants to estimate power, not relative power. Jerry -- Engineering is the art of making what you want from things you can get.
Reply by ●June 25, 20112011-06-25
