<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Dear Crispin, stovers,<div class=""><br class=""></div><div class="">So if I understand what you are saying the sample is diluted enough such that only single particles are measured and they are not entered into the detector as in groups. I’m thinking more of dirty water that I am familiar with. The dirty water is paced into a vial and tilted (shaken) just before making a measure of reflected light from the group. But if we want counts the water is diluted and number of each particle determined. This to count cells etc.</div><div class="">is this much the same as measuring particles in air? </div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">wondering:</div><div class=""><br class=""></div><div class="">Does white colored particles give more reflected light than black particles?</div><div class=""><br class=""></div><div class="">What is the converting factor going from reflected light to mass? </div><div class=""><br class=""></div><div class="">When the reported value is 2.5 um is there a range like from 3um to 2um and above and below that not included?</div><div class=""><br class=""></div><div class="">Is the angle of reflected light used to determine the size of the particles? </div><div class=""><br class=""></div><div class="">thanks</div><div class=""><br class=""></div><div class="">Frank</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""> </div><div class=""><br class=""></div><div class=""><br class=""><div apple-content-edited="true" class="">
Frank Shields<br class=""><a href="mailto:franke@cruzio.com" class="">franke@cruzio.com</a><br class=""><br class="">
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<br class=""><div><blockquote type="cite" class=""><div class="">On Jun 15, 2015, at 11:12 AM, Crispin Pemberton-Pigott <<a href="mailto:crispinpigott@outlook.com" class="">crispinpigott@outlook.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; font-family: Helvetica; font-size: 18px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Dear Dave<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">>Looking at the Speck product description and the Syhitech DSM501A documentation (such as it is), I wonder if/how Speck can differentiate several 2.5-micron-diameter particles from a solitary particle that is 10s or 100s of microns in diameter.<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">The reflection off each particle is measured according to its strength with a detector. Small particles give a very small signal. This is calculated to give an effective diameter, as if all the particles are round, known as the<span class="Apple-converted-space"> </span><i class="">aerodynamic diameter</i>.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""> </span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">The particles are fed through at a very high speed – perhaps 20 metres per second in a thin air stream sheathed with a clear air stream for a total diameter of about 1mm. With a device as simple as the Speck the whole thing is miniaturised but works on a similar principle at a low speed.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""> </span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">When only PM2.5 is wanted, a cyclone can be attached that removes particles larger than PM2.5. There are in fact very few particles in the range 2-3 microns which is why that size was chosen. Being a little off makes no different to the total count.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""> </span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">Most particles from a solid fuel fire are below 0.5 microns unless there is a fan blowing up ash in which case it tends to be PM4 or so, well away from PM2.5.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""> </span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">Regards<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">Crispin<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; 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