user53509: In the AM2302 datasheet at page 3, table 4, it gives min, typ and max values for Rpu (that the pull-up resistor as it says verbatim) being 30K, 45K and 60K ohm respectively.
Elsewhere in the same table it gives figures for Rp (no u) < 25K ohm.
What is the difference between Rpu and Rp here, and how should the two rows be interpreted?

user30198: The datasheet is as inaccurate as the sensor itself and it is even worse than you think!
In that datasheet is also written: "usually require an external about 5.1kΩ pull-up resistor".
In the datasheet is also mentioned that the output signal can go up to 8 mA for a high output and minimal 10 µA low output. The 10 µA means that the pullup resistor should be 500k or more. That is not correct.
In this datasheet is a picture with 1k.
In this Chinese datasheet is a picture with 5k.
I ran that Chinese datasheet through Google Translate, but that did not help.
Conclusion: The datasheet is not reliable.
You can do as everyone else: use a 10k resistor for short wires, and try 4k7 for longer wires.
That is not the only problem. Some DHT libraries create a shortcut on the data signal.
The AM3202 is not accurate for measuring the humidity. If you want to avoid trouble, then use a better sensor.
A sensor from Bosch is a good choice (for example the BME280 or BME680). Bosch makes datasheets that are reliable. Those sensors from Bosch operate at 3.3V, if you are going to connect that to a 5V Arduino board, then you need level shifters for the signals.

53509: <p>In the <a href="https://akizukidenshi.com/download/ds/aosong/AM2302.pdf" rel="nofollow noreferrer">AM2302 datasheet</a> at page 3, table 4, it gives <code>min</code>, <code>typ</code> and <code>max</code> values for <code>Rpu</code> (<code>that the pull-up resistor</code> as it says verbatim) being <code>30K</code>, <code>45K</code> and <code>60K</code> ohm respectively.</p>

<p>Elsewhere in the same table it gives figures for <code>Rp</code> (no <code>u</code>) &lt; 25K ohm.</p>

<p>What is the difference between <code>Rpu</code> and <code>Rp</code> here, and how should the two rows be interpreted?</p>
 30198: <p>The datasheet is as inaccurate as the sensor itself and it is even worse than you think!</p>

<p>In that datasheet is also written: "usually require an external about 5.1kΩ pull-up resistor".</p>

<p>In the datasheet is also mentioned that the output signal can go up to 8 mA for a high output and minimal 10 µA low output. The 10 µA means that the pullup resistor should be 500k or more. That is not correct.</p>

<p>In <a href="https://cdn-shop.adafruit.com/datasheets/Digital+humidity+and+temperature+sensor+AM2302.pdf" rel="nofollow noreferrer">this datasheet</a> is a picture with 1k.<br>
In <a href="http://www.adafruit.com/datasheets/DHT11-chinese.pdf" rel="nofollow noreferrer">this Chinese datasheet</a> is a picture with 5k.<br>
I ran that Chinese datasheet through Google Translate, but that did not help.</p>

<p><strong>Conclusion: The datasheet is not reliable.</strong></p>

<p>You can do as everyone else: use a 10k resistor for short wires, and try 4k7 for longer wires.</p>

<p>That is not the only problem. <a href="https://github.com/adafruit/DHT-sensor-library/issues/48" rel="nofollow noreferrer">Some DHT libraries create a shortcut</a> on the data signal.</p>

<p>The AM3202 is not accurate for measuring the humidity. If you want to avoid trouble, then use a better sensor.<br>
A sensor from Bosch is a good choice (for example the BME280 or BME680). Bosch makes datasheets that are reliable. Those sensors from Bosch operate at 3.3V, if you are going to connect that to a 5V Arduino board, then you need level shifters for the signals.</p>
