Patent ID: 8471721

Claim:
A server rack, comprising: a main body configured for receiving a plurality of blade servers therein; an electronic scale comprising: a pressure sensor supporting the main body and configured for measuring pressure from the main body to obtain a pressure signal, a microcontroller configured for analyzing the pressure signal to calculate total weight of the main body and the blade servers, and an amplifying circuit electrically connected to the pressure sensor and the microcontroller, and configured for amplifying the pressure signal of the pressure sensor, and sending the amplified pressure signal to the microcontroller, wherein the amplifying circuit comprises a first operational amplifier, a second operational amplifier, a third operational amplifier, a first capacitor, and a second capacitor; the first operational amplifier comprises a first positive input terminal, a first negative input terminal, and a first output terminal; the second operational amplifier comprises a second positive input terminal, a second negative input terminal, and a second output terminal; the third operational amplifier comprises a third positive input terminal, a third negative input terminal, and a third output terminal, the first positive input terminal is connected to the first signal terminal, the first negative input terminal is connected to the first output terminal, the first output terminal is also connected to the third negative input terminal, the first positive terminal is also connected to the first negative input terminal through the first capacitor, the second positive input terminal is connected to the second signal terminal of the pressure sensor, the second negative output terminal is connected to the second output terminal, the second output terminal is connected to the third positive output terminal, the second positive input terminal is connected to the second negative input terminal through the second capacitor, the third positive input terminal is grounded, the third negative input terminal is connected to the third output terminal, the first negative input terminal is also connected to the second negative input terminal; an alarm storing a predetermined weight threshold, the predetermined weight threshold being total weight of the main body and a maximum number of blade servers that the main body can bear, the alarm signaling an alarm when the measured total weight is larger than the predetermined weight threshold.