I recently had to purchase a number of 10r000 precision resistors. I opted for the Vishay VAR Series, which are audio resistors. I had a difficult time even finding out about the VAR series. THEY'RE bulk metal foil type. And quite resonably priced, $15ea. For 0.1% with TCR +(-) 0.05ppm/C, 0C + 60C,
+(-) 0.2ppm/C, 0C + 125C. VCR 0.1ppm/V. Low current noise (1/f-type, pink noise) capacitance/inductance (0.08uH) design, with high linearity.
Load life stability is 0.005%@70C, 2000hrs at 0.4W. Current noise: 0.010uV RMS/V of applied voltage (< -40dB)
Thermal EMF between the leads and resistive element 0.05uV/C. Rise time 1 ns, for virtually no ringing. Thermal and shot noise are distributed through the entire signal band. (White noise)
Product code: 0706, resistive values, 10r000 to 100k000, tolerance 1% to 0.01%, 0.005% aailable. Rated maximum voltage 200, maximum power 0.4W@70C.
One thing I'm not sure about. The cover over the resistive element looks separate from the resistor. Several times in the datasheet it mentions the naked Z-foil design, without encapsulation. I'm not sure if that is a customization, or it is achieved by the design of the VAR Series.
Worthy of note is the Z Series, which have even better specs, but at 2x the cost for comparable specs to the VAR Series. I had a 29-week lead time from Digikey. I don't know if it stocks any of the VAR Series. I think demand exceeds supply. I purchased 10r000 value, which is the lowest availabld, and likely the most costly, all else being equal. 0.1% of 10 Ohm is 10mOhm, which is more difficult to ensure as a tolerance than 0.1% of 10k000 which is 10 Ohms.
I am an analog design engineer. My opinion is that--at 1/2 the cost of the Z-Series--the Vishay Precision VAR Series offers the most bang for the buck in demanding applications. Vishay also has a limited series of precision high-power Kelvin connected resistors (4 leads) that Digikey stocks a few of.
+(-) 0.2ppm/C, 0C + 125C. VCR 0.1ppm/V. Low current noise (1/f-type, pink noise) capacitance/inductance (0.08uH) design, with high linearity.
Load life stability is 0.005%@70C, 2000hrs at 0.4W. Current noise: 0.010uV RMS/V of applied voltage (< -40dB)
Thermal EMF between the leads and resistive element 0.05uV/C. Rise time 1 ns, for virtually no ringing. Thermal and shot noise are distributed through the entire signal band. (White noise)
Product code: 0706, resistive values, 10r000 to 100k000, tolerance 1% to 0.01%, 0.005% aailable. Rated maximum voltage 200, maximum power 0.4W@70C.
One thing I'm not sure about. The cover over the resistive element looks separate from the resistor. Several times in the datasheet it mentions the naked Z-foil design, without encapsulation. I'm not sure if that is a customization, or it is achieved by the design of the VAR Series.
Worthy of note is the Z Series, which have even better specs, but at 2x the cost for comparable specs to the VAR Series. I had a 29-week lead time from Digikey. I don't know if it stocks any of the VAR Series. I think demand exceeds supply. I purchased 10r000 value, which is the lowest availabld, and likely the most costly, all else being equal. 0.1% of 10 Ohm is 10mOhm, which is more difficult to ensure as a tolerance than 0.1% of 10k000 which is 10 Ohms.
I am an analog design engineer. My opinion is that--at 1/2 the cost of the Z-Series--the Vishay Precision VAR Series offers the most bang for the buck in demanding applications. Vishay also has a limited series of precision high-power Kelvin connected resistors (4 leads) that Digikey stocks a few of.
I used these guys for some custom resistors (RIAA circuit). Took just a few weeks to arrive.
https://www.texascomponents.com/store/bmfaudioresistors.asp
https://www.texascomponents.com/store/bmfaudioresistors.asp