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使用毫伏计测量温度时,感温热电偶与毫伏计之间是通过几米甚至几十米的补偿导线连接的,在使用中往往容易忽略毫伏计外接电阻(即外线调节电阻)的配制及调整毫伏计机械零位这两个问题。一、外线路调节电阻的配制众所周知,毫伏计是按一定量程系列生产的,标尺刻度固定,且外线路电阻R外规定为标准值5Ω、15Ω、25Ω。因此,用户在使用时,还必须按所用热电偶内阻R_热和补偿导线电阻R_补,再串接外线电路调节电阻R_调满足如下条件: R_外=R_热+R_补+R_调 R_调是由用户配制的,通常用锰铜丝绕制。其数值必须配得准确,为此尽量能准确地测量出R_热和R_补。其中R_补在实际线路上测得,而R_热应是热电偶在使用温度范围内的内阻值,否则出现误差。例如,铂铑-铂热电偶在常温下其R_热约为1Ω,当温度达到1300℃时,
When using the millivoltmeter to measure the temperature, the thermocouple and the millivoltmeter are connected by a compensation wire of several meters or even tens of meters, and it is often easy to neglect the millivoltmeter external resistance (that is, the external regulating resistor) Preparation and adjustment millivolt mechanical zero these two issues. First, the preparation of the external circuit adjustment resistor As we all know, millivoltmeter is produced by a certain range of series, the scale fixed, and outside the line resistance R is specified as the standard value of 5Ω, 15Ω, 25Ω. Therefore, the user must also use the thermocouple R_ resistance and compensation wire resistance R_compensation, and then connect the external circuit adjusting resistor R_ with the following conditions: R_out = R_heat + R_ Make up + R_ tone R_ tune is prepared by the user, usually with manganese copper wire wound. The value must be equipped with accurate, to try to accurately measure R_ heat and R_ complement. Which R_ complement measured in the actual line, and R_ thermocouple thermocouple within the temperature range of the internal resistance, or error. For example, platinum rhodium - platinum thermocouple at room temperature R_ heat about 1Ω, when the temperature reaches 1300 ℃,