Agilent Technologies U2802A manual Other Features

4	Product Specifications
		Overvoltage protectioni	TC Modeii
			• Common mode: ±17 V (TC+ and TC– with
			respect to GND)
			• Differential mode: ±7 V (Differential voltage
			between TC+ and TC–)
			Bypass mode
			• ±20 V (TC+ input with respect to GND)
			Power Off Mode
			• ±11 V (TC+, TC– input with respect to GND)
		Input impedance	> 1 GΩ
		Input bias current	±2.5 nA max
		Input offset current	±1.5 nA max
		Gain drift	60 ppm / °C max
		Offset drift	1 µV / °C max
		Filter cutoff frequency (–3 dB) (thermocouple	4.0 Hz
		mode)
		Filter type (thermocouple mode)	Low Pass RC Filter
		OTHER FEATURES

Recommended warm up time

30 minutes

iThe overvoltage protection levels specified above indicate the maximum voltage each input pin can tolerate without resulting in any damages. However, prolonged exposure to these levels may affect device safety and reliability. Hence, it should be avoided where possible.

iiOn the channels configured for thermocouple mode, the TC+ and TC– pins can tolerate up to ±17 V of differential voltage for a few minutes. However, exceeding ±100 mV voltage range on these channels can cause additional current to be drawn from the device’s power supply regulators, which may damage the device if multiple channels are overdriven for prolonged periods. This

applies to the case where a voltage source is tied across the TCn+ and TCn– pin. Voltage sources greater than ±100 mV should be tied to TCn+ and GND (floating source), or TCn+ and TCn+1+ (grounded source), and have the channels set for bypass mode. Refer to Figure 2-5on page 32.

50 Agilent U2802A 31-Channel Thermocouple Input User’s Guide