TaN film SMT also attracted to rare earth. And $20.40 later, find that it is indeed as Sy indicated--the ends of the Susumu/Vishay are attracted.
Of TH resistors, "superb PRP 9372 audio grade metal films from Precision Resistive Products" very attracted even the body. Of the resistors I tested, only Holco resistors are standoff-ish.
(Least now I know which resistor will make my audio arc welder sound best
. . . jk)
Of TH resistors, "superb PRP 9372 audio grade metal films from Precision Resistive Products" very attracted even the body. Of the resistors I tested, only Holco resistors are standoff-ish.
(Least now I know which resistor will make my audio arc welder sound best
. . . jk)It's used in some automated assembly processes.
Quite a few components have magnetic leads as well, not just the body. Capacitors, glass body diodes and resistors.
Long ago I was developing broadcast tv monitors. We had a horrible kink in the display that was eventually traced to a TI 741 in the psu with a ferrous lead frame picking up the field from the scan coil. Changing to another vendor solved the problem.
Iron leads can make good low frequency antennas
Iron leads can make good low frequency antennas
Yes in a colour monitor with HT, line transformer maybe, but these days with our awareness of emc etc, I have never known an engineer these days to be concerned with some slight magnetism in components, apart from transformers and inductors, and when designing a PCB or an assembly you keep sensitive circuitry away from such things.
A CRT based TV can generate strong fields up to a few metres away.
Badly layed out power amp bridge rectifiers cause strong magnetic fields.
Switched mode psus often have air gapped storage inductors that radiate strongly
Valve amps with C core chokes/output transformers with an airgap are also sources
Badly layed out power amp bridge rectifiers cause strong magnetic fields.
Switched mode psus often have air gapped storage inductors that radiate strongly
Valve amps with C core chokes/output transformers with an airgap are also sources
Yes, its EMC, you design products and lay out PCB's to mitigate these problems. There is a whole range of info and advice on combatting EMC, from Henry Otts books and web site, to the EMC compliance club in the UK, FCC CE etc.
So what I am asking is what effect would magnetism (be it Ferro-, para- dia-) in some components have in a correectly designed and layed out circuit, taking into account EMC design principles.
The h field will induce current in copper tracks as well as iron, maxwells stuff.
So what I am asking is what effect would magnetism (be it Ferro-, para- dia-) in some components have in a correectly designed and layed out circuit, taking into account EMC design principles.
The h field will induce current in copper tracks as well as iron, maxwells stuff.
One way to figure out if they are carbon or metal film resistors is their temperature coefficient. In general, the resistance of metal film resistor will increase by increasing temperature (i.e PTC or positive temperature coefficient), while carbon film resistors will see their resistance drop by increasing temperature (i.e. NTC).
Some, it is a very simple test: measure the resistance of the resistor while you heat it up (keep a solder iron very close to it, the value will change in seconds....). Carbon film will drop fast.
So copy-paste info text from www:
Temperature coefficient
The value of a resistor is dependant on the length, cross sectional area and resistivity of the resistive material it is made from. The quoted value of a resistor however is actually given as "So many ohms at a particular temperature". This is because the temperature of the resistor also affects its value.
The change in resistance due to a change in temperature is normally quite small over a particular temperature range. This is because the manufacturer has chosen a material having a resistivity not greatly influenced by temperature. That is, the material (and so the resistor) has a low TEMPERATURE COEFFICIENT. In other words, there is only a small change in value per °C. This change in value is normally quoted in parts per million (ppm) so a typical resistor would have, as part of its specification a quoted temperature coefficient such as;
Temperature coefficient: 50ppm/°C
Meaning that the change in value due to a temperature change of 1°C will not be more than 50Ω for every 1MΩ of the resistor's value (or 0.05Ω for every 1KΩ of its value).
The temperature coefficient quoted above would be typical of a metal film resistor. Carbon film types have temperature coefficients typically around 200 to 500ppm/°C
The change in value of a resistor with changing temperature is not very dependent on changes in the dimensions of the component as it expands or contracts due to temperature changes. It is due mainly to a change in the resistivity of the material caused by the activity of the atoms of which the material is made.
Some, it is a very simple test: measure the resistance of the resistor while you heat it up (keep a solder iron very close to it, the value will change in seconds....). Carbon film will drop fast.
So copy-paste info text from www:
Temperature coefficient
The value of a resistor is dependant on the length, cross sectional area and resistivity of the resistive material it is made from. The quoted value of a resistor however is actually given as "So many ohms at a particular temperature". This is because the temperature of the resistor also affects its value.
The change in resistance due to a change in temperature is normally quite small over a particular temperature range. This is because the manufacturer has chosen a material having a resistivity not greatly influenced by temperature. That is, the material (and so the resistor) has a low TEMPERATURE COEFFICIENT. In other words, there is only a small change in value per °C. This change in value is normally quoted in parts per million (ppm) so a typical resistor would have, as part of its specification a quoted temperature coefficient such as;
Temperature coefficient: 50ppm/°C
Meaning that the change in value due to a temperature change of 1°C will not be more than 50Ω for every 1MΩ of the resistor's value (or 0.05Ω for every 1KΩ of its value).
The temperature coefficient quoted above would be typical of a metal film resistor. Carbon film types have temperature coefficients typically around 200 to 500ppm/°C
The change in value of a resistor with changing temperature is not very dependent on changes in the dimensions of the component as it expands or contracts due to temperature changes. It is due mainly to a change in the resistivity of the material caused by the activity of the atoms of which the material is made.
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