直流纳伏以下放大器

2016年03月21日 09:40    发布者:泓睿

详细介绍:
EM A20是一种可以对毫微伏进行测量的敏感的放大器。根据设计,它被用在校准、低温研究和仪器系统内。A20的生产是为了满足EM零位探测器内仪器具备类似灵敏度的要求。它的短路输入很低,等同于低于10Ω的噪声阻抗,借助很短的响应时间给出了100μV的解决方案。对于A20能够运行的电源电阻范围,我们给与了特别关注。对于电源电阻针对噪声电压波形,我们开展了研究。这一研究表明了它的重要性。“电流”和“电压”噪声线路从300K被外推至3K。当A20处于室温条件下时,它可以在氮点下对电源进行有效的测量,同时又不提高噪声水平。从1×102至1×106之间,存在着4种增益设定。借助25条渠道的D型连接,施加各种等级的电压,以选择各种增益设定。这种D型连接可以对滤波器进行控制,并能连接输出,提供电源并发挥其他的作用。在有要求的情况下,让用户对增益设定进行定义是可能的。在这种情况下,在外部安装增益设定阻抗,用户也能对其实施控制。4个增益控制线路保持开路,增益阻抗也在连接器上的点10和11之间连接。在机箱边缘可以接入控制器,以将补偿电压和电流清零。输入连接在铜制终端之上,螺帽和垫圈都由相同的高纯度铜支撑,因此热电势效应就被最小化了。A20被安装在一个重型高导磁率合金内,输入单元被装在一个重型计量高导磁率合金双屏之中。
The EM model A20 is a very sensitive amplifier for making sub nanovolt measurements and is designed to be used in calibration, cryogenic research and instrumentation systems.The A20 has been produced in response to requests for an amplifier of similar sensitivity to those used in EM null detectors, having a very low short circuit input equivalent noise resistance of less than 10 ohms, giving resolution of a hundred picovolts with comparatively short response time.Particular care has been taken with respect to the range of source resistance with which the A20 can operate. This parameter is very important when measuring cryogenic sources. A study of the graph overleaf of source resistance against noise voltage will show the importance of this. The `voltage' and `current' noise lines have been extrapolated from 300 deg K to 3 deg K. and it can be seen that the A20, while remaining at room temperature can efficiently measure a source at helium temperature, without adding significantly to the overall noise.There are 4 gain settings from a thousand to a million and these are selected by voltage levels applied via the 25 way `D' type connector, which has a control for a filter, as well as carrying the output connection, the power supply and other functions. It is possible to have user defined gain settings if required, in which case the gain determining resistors are mounted externally and are under the user抯 control. The four gain control pins are left open circuit and the gain resistor is connected between pins 10 and 11 on the 慏&O5533; connector.Controls are accessible at the edge of the case for nulling offset voltage and current.The input connections are made on copper terminals with nuts and washers all made from the same high purity copper, so that thermal emf is minimised.The A20 is mounted in a heavy duty mumetal case, and the input unit is enclosed in doublescreens of heavy gauge mumetal.



A20型直流毫微伏放大器噪声:同等的噪声阻抗低于10Ω。噪声电压取决于带宽,也就是,上升时间为恒定的10秒,峰峰噪声电压为250nVp-p。Noise.Equivalent noise resistance less than 10 ohms. Noise voltage depends on bandwidth e.g. rise time constant 10 seconds gives peak to peak noise voltage of 250 picovolts.

补偿电压借助在机箱边缘带有10个刻度的电位计将电压调整为0度。温度系数优于300pV/℃。Offset Voltage.Adjustable to zero by a ten turn potentiometer accessible at the the edge of the case. Temperature coefficient better than 300pV per degree C.

补偿电流借助在机箱边缘带有10个刻度的电位计将电压调整为0度。温度系数优于10pV/℃。Offset Current.Adjustable to zero by a ten turn potentiometer accessible at the edge of the case. Temperature coefficient better than 10pA per degree C. 增益

有4个增益设定,分别为1000,10000,100000,1000000。这些增益在内部设定,精确度为0.02%,取决于本底噪声。温度系数为5ppm/℃。Gain.There are 4 gain settings 1K, 10K, 100K, and 1M. These gains are set internally.Accuracy 0.02%, subject to noise floor.Temperature coefficient 5ppm per degree C.

滤波器可以选择一个能够给出下列上升时间常数的滤波器。Filter.A filter may be selected which gives the following rise time constants.

范围 时间常数1000: 无增加10000: 100毫秒100000: 1秒1000000: 10秒Range     Time Constant1K:          No Increase10K:        100 milliseconds100K:      1 second1M:         10 seconds

输入阻抗在阶跃输入函数3秒之后,大于30000000Ω。随着时间增长到1GΩ,参见输入阻抗图。Input Impedance.Greater than 30 Megohms, 3 seconds after an input stepincreasing with time to 1 Gohm, see input impedance graph


电源电阻A20严格遵循电源热噪声特性,电源阻抗的范围在10Ω到100000Ω之间。当阻抗低于10Ω时,噪声便会不断下降,使得阻抗最后低至0Ω。当电阻在1000000Ω之上时,噪声电压将上升至热噪声特性之上,上升幅度为10进制的10dB。输入噪声特性图展示,如果“电压”和“电流”噪声线被推出,那么A20将使得总体噪声水平提升大约1K源电阻。Source Resistance.The A20 closely follows the source thermal noise characteristicwith sources resistances of 10 ohms up to around 100 Kohms.With source resistances below 10 ohms, the noise is substantiallyconstant down to zero ohms. Above 100 Kohms, the noise voltageincreases over the thermal noise characteristic by about 10 dB perdecade of source resistance. The input noise characteristic graphshows that, if the `voltage' and `current' noise lines areextrapolated as far as the thermal noise line for heliumtemperature, the A20 still adds insignificantly to the total noise ataround 1K source impedance.

输入等级A20可接受的输入电压高达2mV。高达2V的输入电压将不会造成损害,如果输入电压在任意时间段出现饱和现象,那么将会出现热补偿的情况,因此需要一定的时间以降低到nV的等级。Input Level.The A20 will accept input voltage up to 2mV. Input voltage up to 2volts will not cause damage, but if the input is saturated for anylength of time, there may be a thermal offset, which could taketime to reduce to sub nanovolt levels.

输出等级A20将提供一个±3V的输出,并将载荷提高至5mA.Output Level.The A20 will provide an output of plus or minus 3 volts and candrive loads of up to 5mA.

连接器A20的输入连接器为纯铜终端,带有同样材质的螺帽和垫圈。螺纹为2BA(直径为4.8毫米)。应当使用低热电磁场未镀锡的铜线实施输入连接工作。在实际工作中,新的、未弯曲的、被细致剥除绝缘的变压器线可满足要求。Connectors.The input connectors for the A20 are pure copper terminals withnuts and washers made from the same material. The threads are2BA (4.8mm diameter)Input connections should be made using low thermal emf untinnedcopper wire. In practice, new, unbent transformer wire,carefully stripped of insulation, is satisfactory.

D25 插头连接插头功能1、滤波器2、增益 1M3 、增益 100K4 、增益 10K5 、增益 1K6 0v7 电源负压8 电源正压10 直接输出11 反馈15 滤波输出18 信号 0V19 机箱插头外罩被连接至A20机箱。机箱和0v.之间的绝缘最小为10GΩ。为了对增益和滤波功能实施控制,应当将选定的销钉连接至+5V。所有未使用的销钉应当保持开路。D25 Plug Connection.Pin Function1 Filter2 Gain 1M3 Gain 100K4 Gain 10K5 Gain 1K6 0v7 Supply Negative8 Supply Positive10 Direct Output11 Feedback15 Filtered Outpu18 Signal 0v19 CaseThe plug outer shield is connected to the A20 case.Isolation between case and 0v. 10 Gohms minimum.For control of gain and filter functions, the appropriate pin shouldbe connected to + 5 volts.

电源最小 ± 5.5 V, 最大 ± 8 V。常规电源± 6 V。静止电流要求 1.5mA。当放大器在 1K的范围且出现全刻度输入的情况时,电流要求可以提高至4mA。Power Supply.Minimum +/- 5.5 volts. Maximum +/- 8 volts.Nominal supply voltage +/- 6 voltsCurrent requirement 1.5 milliamps quiescent.This may increase up to 4 milliamps when the amplifier sees a fullscale input on the 1K range

固定要求M4中心设有4个洞,尺寸为8.4英寸和5.6英寸。Fixing.4 holes required M4 centres 8.4 inches by 5.6.inches.

规格和重量长度 8.75英寸(222毫米)宽度 6 英寸 (152.4毫米)包含终端的深度 3.7 英寸(毫米)重量 9 磅 (4 Kg)Dimensions and Weight.Length 8.75 inches (222mm)Width 6 inches (152.4mm)Depth including terminals 3.7 inches (95mm)Weight 9 lbs (4 Kg)有意者联系18500613848张先生