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98 Threads found on edaboard.com: Junction Temperature
Thermocouple voltage can't be processed by PIC directly. Need a DC amplifier with gain of 200 to 250 to fit the 5 V ADC range, also a temperature sensor for cold junction compensation.
There are ADC with internal PGA that can measure thermo couples. ADS1118 has e.g. about 0.2 K resolution and a few K absolute accuracy, also an internal temperature sensor suitable as cold junction reference. That's not mind blowing but suitable for many applications.
Hola I am using a TPS62122 stepup converter. This have junction to ambient thermal resistance set to 114.4°C/W and a max load of 75mA. Am I correct that on a PCB which have no extra cu for thermal disipation that when this converter is generating a 3.5V form a 12V supply, the temperature may reach as high as 90°C @65mA load when ambient tempera
Inserting a different metal (e.g. connector, terminal strip) into a thermocouple wire will only generate an additional thermo-electric voltage if both end junctions are at different temperatures. This can of course happen, if the connector is mounted in an enclosure wall with different in- and outside temperature. For this reason, dedicated (...)
Any silicon semiconductor junction forward voltage has a temperature coefficient of about -2 mV/K. Asking for a more stable voltage drop is simply ignoring laws of physics. It makes sense to ask for devices with less type variation of forward voltage, specific leakage or current gain characteristics. But forward voltage temperature (...)
Hi Could someone please help me with a problem. I have a PCB that fits in an ABS box and is to be completely potted, top and bottom. I am investigating device failure modes, as I need to ensure that the outside surface temperature does not reach 135C. I've worked out that one SOT23 device may reach a junction temperature of 150C, (...)
Have to agree with Barry here. There are many limitations to accuracy that include the accuracy of cold junction correction, plus the purity of the metal alloys in the thermocouple, plus the accuracy and calibration of the electronic amplifier. Thermocouples have a great many advantages, but absolute accuracy is not one of them. Your best bet m
Max junction temperature = 150*C, use 120 for safety. Tambient = 40 *C, so you have to dissipate 10 Watts across a temperature of 110*C. The thermal resistance of the junction to case is 6.5*C/W, So the case of the transistor will be at 65*C less then the max, i.e. 120- 65 = 55*C. So the heatsink will have to dissipate 10W (...)
Dear friends , I need to make a j type temperature controller . Please suggest me how to proceed , never used one before . 1. I need circuit used for j type thermocouple signal amplification using opamp op07 and diode for cold junction compensation , I have seen temperature controllers using thermocouples in mkt and they use a diode (...)
I am able to read temperature accurately using MCP9600. Its a Thermocouple EMF to temperature Converter. The MCP9600 digital temperature sensor comes with user-programmable registers which can be used to detect multiple temperature zones. I.e. it can be configured to detect when the Hot junction of a (...)
A semiconductor junction conducts better when it is warmed. Therefore its forward voltage becomes reduced. You cannot change it so don't ask why.
​ Electronic component always goes wrong because of exceeding junction temperature, that caused by two reasons: 1. the calorific power of itself is too high; 2. Filling with air in the electronic component that result in bad heat conductivity. At present, there are not any ways to solve this problem except that removed
you really need to use that "sleeve of copper braid" to be your heat sink. otherwise the diode will quickly fail. It is just a silicon diode, and the gold metallization will diffuse into the silicon body if the temperature gets too hot, and the diode will eventually short out. I would mount the diode right at the junction of the shield and radi
Hello everyone, I am doing Thermal Analysis of my device and I need to calculate thermal resistance between junction and Case of my device. All I given in datasheet is junction temperature and Base plate temperature. There is no information given about thermal resistance between junction and Case. So, (...)
junction refers to semiconductor junction (e.g. of a transistor), in other words the chip temperature. The "junction" or chip is the heat source and obviously the hottest point in chain. It's also the most sensitive point.
Enclosed cases are always critical thermal designs. Apart from having to use a large fan to ensure equal distribution of air flow through the greatest possible internal surface of the cabinet, it may also be necessary an additional small fan over the hottest components in order to prevent the junction temperature exceeds the specified limit.
Hello, I've always limited junction temperature of such diodes to 110 deg c in the past, but is it ok if we run the MUR840 diode with Tj=150 degC? The datasheet suggests we can. Its got 4A average in it. MUR840 datasheet
Tj max will specify the max junction temp, the device can withstand ... you have to look into the graphs in DS to see what's the allowed rms current at this Tj. That means you may not be able run at max power what you need at this temp of junction. Also, with or without heat sink, you can calculate what can be the ambient temp for the device operat
It's normally mentioned in the data-sheet of the transistor as SOA ( Safe Operating Area ). Or Rth should be given to calculate package temperature.For instance Rth=500 K/W ( From junction to Free Air) for BC857.If power dissipation 150mW, if ambient temperature is 25C, junction temperature will be 75C so (...)
It doesn't generate an analog signal. The report is entirely digital. I think the earlier versions of the device used two oscillators, one temperature stabilized, the other temperature dependant, the difference in frequencies was used to produce the numeric result. Later versions used an internal bandgap reference, PN junction to sense (...)
hello, on IRFB7540 (and many others) datasheet it indicates junction to ambient temperature = 62C/W what does this mean ? does it mean that if I touch the mosfet package I would feel 62 * P(dissipated) degrees ? 8-O let's say I dissipate only 3 watts
I am using K-Type Thermocouple with Ungrounded junction. all the required circuits such as, cold junction compensation, filtration and amplification is working perfectly. My problem is at room temperature Sensor is showing same temperature of 0.5 degree greater than Thermometer. ( Room Temp aroung 26 to 28 *C). But at lower (...)
Hello Everyone, I have the following Spec junction temperature 125C Power Consumed:2W Ambient temperature=60C What parameter should i consider in the datsheets of MOSFET such that the selected MOSFET will meet the Spec defined for temperature. Regards Santhosh V The parameters you consider are mechanical thermal r
Can you define all input/output parameters for the design? ...besides 46.4V at 3.52A Then the test criteria for performance comparison will be obvious. e.g. Recall my formula for ESR of a diode? temperature drift? what about response time or junction capacitance? ambient temp? overshoot?
Hello, Page 5 of the attached datasheet gives forward voltage measurements for the UV LEDs at 350mA , and says it's done at an ambient temperature of 25 degC...however, do you know what was the junction temperature for these measurements?. I mean the measurment might have been done by simply pulsing the leds with 350mA for 1millisecond (...)
you're reliability guru's scare easily. SiC is very reliable because it has such low losses and junction temperature easily over 200C. i said EASILY. i built a 50kW inverter with SiC at 600V and hit 98% efficiency over entire range. that was like 7 years ago or so. i also met MIL-STD 704 & 160 for noise. this competition has no price or r
All 78xx regulators has an internal thermal shutdown if the temperature gets too high. This is an emergency shutdown, and acts as a safety measure. The thermal resistance from junction to air is around 60 C/W, so it means that you can have less than 1.5W disipation from a chip with no cooling. For an output of 8V from a 24V supply you can only
Dear friends , I need to make a j type temperature controller . PLease suggest me how to proceed , never used one before . 1. I need circuit used for j type thermocouple signal amplification using opamp op07 and diode for cold junction compensation , I have seen temperature controllers using thermocouples in mkt and they use a diode (...)
Something's not right. If you have 184 deg-C/W and .24 W, rise should be 44 degrees. You're showing 34 degree rise. I would go with worst case, so your junction would be at 94 worst case. Maybe a little high for my tastes, but it's within spec. If this is going in a space ship or medical equipment, I'd look to cool it more. For this device, y
"satisfactorily" depends. As cold junction compensation is not use in the application under discussion, an error of 30C-40 C should be expected under different atmospheric conditions. I once made a digital thermometer and control for a four stage compressor. Requirement was to be accurate within 5 degree C from 0-700C. It used TL07
Hi, All, I am very confused on the failure test of power devices. As well know, the short-circuit capability test of power mosfets/igbts can be used to determine and design the fault response time of a overcurrent protection circuit. 1. So how about the avalanche capability test of power mosfets/igbts? To determine and design a fault response
It is the temperature of the substrate (the PCB material) using a predefined trace layout. The heat mostly spreads out via the leads, and these are thermally connected to the PCB. So, is that the same as Tj (junction temp)? Wait, you mean PCB substrate? That's a weird spec. As you say, heat is conducted by th
Hi, I am using LM317MQDCYR from TI as a current limiter in my circuit. I want to estimate the junction temperature of LM317 when it is limiting the current. I have measured the top surface temperature rise above ambient of LM317. I have Θja from the datasheet of LM317 and maximum power being dissipated in LM317. I can use the formula (...)
Heasink temperature is not the concern.Instead, junction temperature should be considered. By doing a backward calculation, you can find the junction temperature if you know thermal resistances of Heatsink to Package (including insulator,mounting plastics,other mechanical parts etc),Package to Die,Die to (...)
junction capacitance tends to rise with temperature and drive strengths drop, so raising available current can compensate this (with the -right- proportionailty).
You select a heatsink as determined from the power dissipated by the LED, the highest ambient temperature, and the maximum LED junction temperature (Tj) you want (should be below the maximum allowed for good reliability). From this, and the thermal impedance calculation given by schmitt trigger above, you determine the thermal resistance to (...)
is the average gate power dissipation what determines how many W it can handle? Not at all. Gate power dissipation will be small in a reasonably designed circuit. It's total power dissipation, thermal resistance, maximum triac and ambient temperature that sets the maximum current. junction to free air thermal resistance is respo
I have the equipment 8pcs thermocouples K. I need to be connected to the PCB with MCU, cold junction compensation with software on the basis of temperature connectors. I have two questions. 1. How to solve the Isothermal Block that all eight connectors have the same temperature and was used one temperature sensor? Cheap (...)
The Applicati on Note AN 2012-03 "Datasheet Explanation" says referring to the avalanche characteristic curve (Figure 13 in the present datasheet): Operating MOSFET under the conditions below the curve is allowed with consideration of the maximum junction temperature. In so far the operation is permitted, and there are in fact m
i need the circuit diagram for cold junction compensation for a thermocouple using lm35. i want to measure the temperature form 0 to 100 degree Celsius. can anybody help me plz.......................!
I want to better understand the nature of the increase in npn collector current with increasing temperature. For Vbe held constant we know that this current approximately doubles with every 10 degree C increase in temperature. I believe there are two sources of this current increase and that they add to each other (they are in the same directio
i guess problem is with the reference temperature as its cold junction compensation doesn't wok in the box. so i figured that it has some extra pins and some of them are related to cold junction compensation but the datasheet didnt talk about it. so any idea how i can feed it with a reference temperature via lm35 or some (...)
Hello, If anyone has experience with Integrated Linear Technology LT3652 from Linear Technology. I've done a battery charger LT3652.. I wonder if it is normal so hot I checked with an infrared thermometer and reaches about 54℃. I wonder if it is normal. Although the data sheet provides as follows: Operating junction: -40T
Vishay has a thermal SPICE model to calculate the dynamical junction temperature. AN609 is explaining the method They have also a thermal simulation tool, but I didn't use it yet.
Dear friends what is the cold junction compensation in thermocouple and if i want to measure temperature by thermocouple using 89c51 then which ic should i use for cold junction compensation. if someone have schematic then it will be strongly appreciated.
if you want measure temperature you can use a PN junction diode either in the forward biased condition or in the reversed biased condition in the forward condition the voltage drop across diode would be reduced by 2.5mV/oC in the reversed condition the reverse current thro' the diode would increase
hi, as i understand you have a sensor (?) that has the dependency Uout = f (t) and that sensor (or measuring circuit ?) is supplied with VDD , and your worry is that the system could be Uout = f (Vdd ( f (t) ) ) ? :?: Then try to stabilize VDD , than your system will became Uout = f (t)|at VDD = ct. - - - Updated - - -
The components that may operate around 200C will be absolutely "Compound Type" e.g. GaAs, InP fact 175C is max. permissible junction temperature for these type of components and a special cooling sytem should be developed to decrease junction temperature such as gas or water cooling system. Silcon and its derivatives don't (...)
Dear amu_cpln, if I use a type B thermocouple, which gives 0V between 0 °C and 50 °C, is needed the cold junction compensation? if yes what is its temperature coefficient? Thank you for reply. Roberto
I don't see any reasonable reason for the bulk-drain junction to leave the linearized region: when the input is 3.3V , the bulk-drain junction is just 1.8V (in reverse) -- no motive for any non-linearity. I guess this is a general warning generated for non-standard voltage levels, not dedicated nor reasonable for your application. And a negative bl