# Why would a part be available as 4.99k and 5k?

I was looking at chip resistors, and came across the MORNTA1001AT5, which comes in many resistance values. The resistor tolerance is 0.1%, so what is the logic of having the part available in both 4.99k and 5.0k versions? Generally, if you needed accuracy like that, you'd use smaller parts as they are easier to match, so I have no idea why there would be a 4.99k and 5k version. I'm just trying to determine if I'm missing something fundamental.

Edit: Could I get an example of where a 0.1% 4.99k would be used over a 5k at 0.1%?

• If this value exists then there is market demand and use for it. Feb 27, 2020 at 16:21
• 4.99k and 5k are more than 0.1% apart from each other. So if you really want 5.00k and not 4.99k and you really need it 0.1% accurate, then you really need the separate part number. Feb 27, 2020 at 16:25
• "Generally, if you needed accuracy like that, you'd use smaller parts as they are easier to match" I do not follow this logic Feb 27, 2020 at 17:05
• perhaps when actually placed 4.99k delivers 5.00k. Feb 27, 2020 at 18:03
• @Anonymous, such as? Feb 28, 2020 at 15:11

The E96 series of preferred numbers contains the 4.99 values.

E96 values (1% tolerance) 1.00, 1.02, 1.05, 1.07, 1.10, 1.13, 1.15, 1.18, 1.21, 1.24, 1.27, 1.30, 1.33, 1.37, 1.40, 1.43, 1.47, 1.50, 1.54, 1.58, 1.62, 1.65, 1.69, 1.74, 1.78, 1.82, 1.87, 1.91, 1.96, 2.00, 2.05, 2.10, 2.15, 2.21, 2.26, 2.32, 2.37, 2.43, 2.49, 2.55, 2.61, 2.67, 2.74, 2.80, 2.87, 2.94, 3.01, 3.09, 3.16, 3.24, 3.32, 3.40, 3.48, 3.57, 3.65, 3.74, 3.83, 3.92, 4.02, 4.12, 4.22, 4.32, 4.42, 4.53, 4.64, 4.75, 4.87, 4.99, 5.11, 5.23, 5.36, 5.49, 5.62, 5.76, 5.90, 6.04, 6.19, 6.34, 6.49, 6.65, 6.81, 6.98, 7.15, 7.32, 7.50, 7.68, 7.87, 8.06, 8.25, 8.45, 8.66, 8.87, 9.09, 9.31, 9.53, 9.76.

So the question is really, who wants a 5.00 value? I've never seen 5 kΩ specifically but I have seen specialty values used for things like ADCs, voltage dividers for multimeter voltage ranges, etc.. Many PLCs use a 250 Ω resistor to convert 4 - 20 mA to 1 - 5 V for their analog inputs. This too is not a standard value.

• Note though, that the OP states that this is a 0.1% resistor, so the table for that series has quite a few more values in it. Feb 28, 2020 at 16:19

The difference between 4.99kOhm and 5kOhm is of the order of 10 ohm, ie a 0.2% change. The resistor tolerance required, as you mentioned, is 0.1%. So if 0.1% tolerance is allowed, a change of 0.2% would disrupt the accuracy. This means that the separate valued resistors are necessary.

The accepted post is correct. All the other values listed in the datasheet except 500Ω, 5kΩ and 50kΩ are part of the E-series of resistors.

Because the resistor is used for "unity gain operational amplifier circuitry" or "voltage references" I assume there are cases where an integer resistor ratio is needed e.g.: 20kΩ / 5kΩ = 4.00. Which otherwise is not easily achievable without combining multiple resistor values in series/parallel.

Therefore they introduced the 0.5 value in addition to the values from the E-series.

• Please don't refer to other posts as "posts above". They are constantly re-ordered based on votes. Best to refer to other posts by name. Feb 27, 2020 at 18:19
• @Mattman944 best to use "share" link available under each post Feb 27, 2020 at 18:29
• I've changed the wordin from "posts above" to "accepted post" in an edit. If this is approved I reccommend checks if @LouisRast matches their intent. Apr 15 at 11:47
• Ah, but @Dan, the OP can change which answer is accepted! Apr 15 at 13:14
• @Transistor this is true, I put something to that effect in my diff comment. There were 24 +1's against the comment that "something must be done", so something quick and minimally disruptive was done, in what seemed to be the generally right direction, in practice top-voted anwsers stabilise and accepteds rarely changed after years. Whereas low-voted answer more often interchange places, altering the context of this answer. I would be more than happy for it to be superseded by a more perfectly coloured bikeshed! Apr 15 at 22:18

5.00 would be part of an E768 series, if anyone made such a range

print(Eseries(192*4))
4.96  4.97  4.99  5.    5.02  5.03
5.05  5.06  5.08


This would represent 0.125% against the Renard scale, where the Eseries numbers are derived from. Now in practice 0.1% resistors appear in the E192 series, even though the E192 series is 0.5% as per Renard scale.

This does mean not all possible values can be realised in 0.1% E192 series, but economics comes into play. Why produce every single resistor value when the larger jump between the tolerance extremes can be managed by design engineers.

• MIL-SPEC uses 1, 2, 3, 4, 5 and so on as normal values do they do exist. Apr 21, 2020 at 19:06

Last year, I designed a Li-on Charger based on LT8490 for the 16S8P battery package. IC demands high-precision resistors for voltage and current configurations. In the input side, 72V is applied and needed to be measured via a voltage divider. Things are getting messy in here. If little valued resistors such as 10 ohms or 100 ohms, then neither IC could handle current applied to pin nor the resistors. I am not a professional but It is obvious that someone uses that rare components you see as unnecessary.