Measuring Heat From Circuit Components : Sometimes TV Gets Too Hot to Handle

Measuring Heat From Circuit Components

By Ed Tittel, published on September 12, 2007
Source: Tom's Guide US | Keywords: sometimes, tv, gets, too, hot, to, handle | Themes: Home Theater

Contents

1. Introduction
2. A Fly In The Ointment Helps The Learning Process
3. Measuring Heat From Circuit Components

3. Measuring Heat From Circuit Components

Our test setup consisted of using the same PC to house a variety of TV capture cards. We cabled the NTSC (also known as standard television, or SDTV) ports up to our local Time-Warner feed, and used an external antenna to feed the ATSC (high-definition digital television) ports where applicable. Older media PCs often include two tuner cards, one for SDTV and another for ATSC. Newer media PCs generally include a single dual-tuner combo card with one NTSC tuner capsule and another ATSC tuner capsule.

Because tuner capsules come in various shapes and sizes (as you’ll see in the table that follows), we decided to create a method for volumetric, apples-to-apples comparison for heat output. We created a synthetic heat measure that we call "heat product" by calculating the volume of the tuner capsule (values are in millimeters in HLW order in the table below), then dividing by the average temperature reading for that device. This produces a single number that you can use as a point of comparison among the various devices you’ll find represented here.

Vendor	Model	Dimensions mm	Avg °C	Heat Product	Volume ratio	Case Temp
ATI	HDTV Wonder	A.13.102.36	39	1224	33.5	38
AVerMedia	M780	N.3.19.25 A.3.19.25	46 46	31 31	1 1	37 37
AVerMedia	MCE A180	A.13.73.40	34	1116	26.6	38
Hauppauge	PVR-150 MCE	N.14.69.36	42	828	24.4	39
Hauppauge	PVR-350	N.14.71.37	41	897	25.8	39
Hauppauge	PVR-500 MCE	N.14.69.36 N.14.69.36	42 42	828 828	24.4 24.4	40 40
Leadtek	WinFast PVR 3000	N.16.72.37	36	1184	29.9	37
N in front of dimensions means the capsule is for NTSC (SDTV), A means ATSC (SDTV)

Whether the heat product is meaningful or not depends on whether you think the volume of the device and its average temperature are necessarily correlated. The scientific method for measuring heat output calls for immersing a heat-emitting item in a specific volume of water at a known temperature and then measuring the temperature repeatedly until the temperature of the liquid in the vessel reaches a steady value. This is something of a problem for electronic devices, particularly when they are best measured in the context in which they’re used - on a computer motherboard! We decided that calculating an average temperature and relating it to volume of the device measured should at least provide some basis for comparison, if not truly representing caloric output. That’s also why we included the volume ratio between the old generation capsules and the new generation capsules in the final column of the preceding table. We also compared internal case temperatures across the board (no other equipment changed between readings) to provide another point of comparison.