Problems with a Sample and Hold:

1. Finite Aperture Time: The sample and hold takes a period of time to capture a sample of the sensor signal. This is called the aperture time. Since the signal will vary during this time, the sampled signal can be slightly off.
2. Signal Feedthrough: When the sample and hold is not connected to the signal, the value being held should remain constant. Unfortunately, some signal does bleed through the switch to the capacitor, causing the voltage being held to change slightly.
3. Signal Droop: The voltage being held on the capacitor starts to slowly decrease over time if the signal is not sampled often enough.