![]() Note that you must first complete the operations in the Multiply By column in order to have the correct factor. So, to convert directly from BTU/h (th) to cal/s (th) you multiply by 0.069998829. Or, you can find the single factor you need by dividing the A factor by the B factor.įor example, to convert from BTU/h (th) to cal/s (th) you would multiply by 0.2928751 then divide by 4.184. To convert among any units in the left column, say from A to B, you can multiply by the factor for A to convert A into W then divide by the factor for B to convert out of W. To convert from W into units in the left columnĭivide by the value in the right column or, multiply by the reciprocal, 1/x.ġ4.653555 W / 0.2930711 = 50 BTU/h ![]() Multiply by the value in the right column in the table below.ĥ0 BTU/h * 0.2930711 = 14.653555 W To simply convert from any unit into W, for example, from 50 BTU/h, just Where S is our starting value, C is our conversion factor, and How to Convert Units of Power and Heat FlowĬonversions are performed by using a conversion factor. By knowing the conversion factor, converting between units can become a simple multiplication problem: in the case of trying to convert an illuminance reading from an area source).Convert among units of power and heat flow. Variances from these assumptions will lead to additional error in the conversion process and could invalidate any results (i.e. The lamp is also assumed to have a clear envelope. This calculator assumes that the light source is a point-source and is isotropic (output is the same in all directions) in nature with the exception of the losses due to the lamp base which are again, assumed, to be about 30 degrees solid-angle. Since this is a measurement geometry conversion - this cannot be helped. Again, this calculator makes several assumptions which directly affect the accuracy of the conversion. ![]() OUTPUT: This is the APPROXIMATE TOTAL WATT OUTPUTof the lamp. In many cases, the default of 30 degrees is sufficient for the expected accuracy of this conversion process. This can be a difficult property of a light source to measure, which is a contributing factor for why any conversions done with this calculator are to be considered approximate and should only be used as a last resort when measuring watts in an integrating sphere is not possible. This is the solid-angle of light that is occluded or blocked by the lamp base.This angle can be any number between 0 (perfectly isotropic source) to 120 degrees. STEP 3: Enter the SHADOW DEGREES (solid angle) in the numerical stepper here. millimeters or inches) you will have to convert these numbers up to meters or feet first. ![]() If you are measuring in units less than meters or feet (i.e. Select whether the distance is in meters or in feet. This number can be entered in decimal format (i.e. STEP 2: Enter the MEASUREMENT DISTANCE at which the reading in Step 1 was taken, in this box. Select what units - W/m 2 or W/cm 2 the measurement was taken in. STEP 1: Enter the ORIGINAL measurement taken in W/m 2 or W/cm 2 with your light meter and sensor here. Any results with this converter must be considered approximate. You must be aware of what each measurement geometry implicitly assumes before conversion. NOTE: Converting between geometry-based measurement units is difficult and should only be attempted when it is impossible to measure in the actual desired units.
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