Using the SLX module of SoundLab for TEF is an excellent way to measure the input impedance of a loudspeaker. There are two methods whereby one may make this measurement.
使用用于 TEF 的 SoundLab SLX 模块是测量扬声器输入阻抗的绝佳方法。有两种方法可以进行这种测量。
The first is by driving the DUT (device under test) through a known resistance and measuring the voltage drop across the DUT. The second is by a direct measurement of the current drawn by the DUT.
第一种方法是通过已知电阻驱动 DUT（被测设备），并测量 DUT 上的压降。第二种方法是直接测量被测设备的电流。

An impedance adapter box is available from Gold Line for the TEF to perform impedance measurements. This adapter places a precision $1\mathrm{k}\mathrm{\Omega }$$1\mathrm{k}\mathrm{\Omega }$1kOmega1 \mathrm{k} \Omega resistor at the output of the TEF in series with the DUT. The input of the TEF is placed across (in parallel with) the DUT.
Gold Line 可提供用于 TEF 的阻抗适配器盒，以执行阻抗测量。该适配器在 TEF 的输出端放置一个精密 $1\mathrm{k}\mathrm{\Omega }$$1\mathrm{k}\mathrm{\Omega }$1kOmega1 \mathrm{k} \Omega 电阻器，与被测设备串联。TEF 的输入端横跨（并联）被测设备。

Figure 1 - TEF Impedance Adapter schematic
图 1 - TEF 阻抗适配器示意图

Figure 2 shows some typical parameters for a full range impedance measurement. Note that the value in the Series Resistance text box must be the same as the value of Rs + the output impedance of the TEF to obtain an accurate measurement.
图 2 显示了全量程阻抗测量的一些典型参数。请注意，要获得准确的测量结果，串联电阻文本框中的值必须与 Rs 值和 TEF 的输出阻抗相同。

Figure 2 - Typical parameters for impedance measurement using a series resistor
图 2 - 使用串联电阻测量阻抗的典型参数

It is possible to connect the DUT directly to the amplifier driving it, unlike the Series Resistance Method described above. For an impedance measurement to be made using this method a current monitor must be employed.
与上述串联电阻法不同的是，可以将 DUT 直接连接到驱动它的放大器上。使用这种方法进行阻抗测量时，必须使用电流监控器。
This will allow a direct measurement of the current drawn by the DUT from the amplifier. Pearson Electronics (http://pearsonelectronics.com/current-monitor-products/standard-current-monitor.htm) makes a line of precision current monitors suitable for this type of measurement. I have obtained very good results using the model 411.
这样就可以直接测量 DUT 从放大器吸取的电流。Pearson Electronics ( http://pearsonelectronics.com/current-monitor-products/standard-current-monitor.htm) 生产的一系列精密电流监控器适用于此类测量。我在使用 411 型时获得了非常好的结果。

One conductor connecting the amplifier to the DUT must be run through the center of the current monitor. Care must be taken to observe the correct orientation of current flow as marked on the current monitor.
连接放大器和 DUT 的一根导线必须穿过电流监控器的中心。必须注意电流监控器上标记的正确电流方向。
Failure to do this may result in the measurement being made with reverse polarity. The Pearson units have a BNC connector that connects to the line input of the TEF.
否则可能导致测量极性相反。Pearson 设备有一个 BNC 连接器，可连接到 TEF 的线路输入端。

Figure 3 - Schematic for use of a current monitor
图 3 - 电流监控器的使用示意图

Figure 4 - Typical parameters for impedance measurement using a current monitor
图 4 - 使用电流监控器测量阻抗的典型参数

Notice the change in the parameters for this configuration. The Drive Voltage is still the actual drive voltage out of the amplifier. This is now the same as the voltage across the terminals of the DUT.
请注意该配置参数的变化。驱动电压仍然是放大器输出的实际驱动电压。现在，它与 DUT 端子上的电压相同。
The Series Resistance, however, must now reflect the output sensitivity (volts/amp) of the current monitor. For the Pearson 411 the sensitivity is 0.100 volts/amp.
不过，串联电阻现在必须反映电流监测器的输出灵敏度（伏/安培）。Pearson 411 的灵敏度为 0.100 伏/安培。

The parameter settings in the figures above were for basic full range measurements. If one wishes to see greater detail in the lower frequency region a separate measurement should be made. This low frequency measurement should have parameters similar to those in Figure 5.
上图中的参数设置用于基本的全量程测量。如果希望看到低频区域的更多细节，则应进行单独测量。这种低频测量的参数应类似于图 5 中的参数。

Figure 5 - Parameters for a low frequency impedance measurement
图 5 - 低频阻抗测量参数

With these parameters the frequency resolution has increased from 44.9 Hz to 7.0 Hz . Quite a bit more detail can now be resolved. Moreover, the data point spacing is now approximately $1\mathrm{Hz}/$$1\mathrm{Hz}/$1Hz//1 \mathrm{~Hz} / point. The parameters in Figure 2 and Figure 4 yield a spacing of approximately $10\mathrm{Hz}/$$10\mathrm{Hz}/$10Hz//10 \mathrm{~Hz} / point. Again more detail can be resolved.
使用这些参数后，频率分辨率从 44.9 Hz 提高到 7.0 Hz。现在可以分辨出更多的细节。此外，数据点间距现在大约为 $1\mathrm{Hz}/$$1\mathrm{Hz}/$1Hz//1 \mathrm{~Hz} / 点。根据图 2 和图 4 中的参数，数据点间距约为 $10\mathrm{Hz}/$$10\mathrm{Hz}/$10Hz//10 \mathrm{~Hz} / 点。同样，可以解析更多细节。

For even greater detail it may be necessary to increase the sweep time.
要获得更多细节，可能需要增加扫描时间。

A rather out-of-the-ordinary use for impedance measurements is to make the measurement using the 3D Test parameters, not the Impedance parameters. This will allow one to investigate resonances in the impedance as a function of frequency and time.
阻抗测量的一个非常规用途是使用 3D 测试参数而不是阻抗参数进行测量。这样就可以研究阻抗随频率和时间变化而产生的共振。
The receive delay is increased for each subsequent measurement so that a later time, after the test stimulus, is examined.
随后每次测量的接收延迟时间都会增加，以便在测试刺激之后的较晚时间进行检测。

Since the Impedance section of SoundLab is not being used for this, the calculations to display impedance are not used. This needs to be kept in mind as the type of measurement configuration will affect what is actually displayed. If one configures the measurement using a
由于 SoundLab 的 "阻抗 "部分不用于此，因此不使用显示阻抗的计算。需要注意的是，测量配置的类型会影响实际显示的结果。如果使用

current monitor, the current delivered to the load will be the measured quantity and this is what will be displayed. This is analogous to an admittance measurement. Accordingly, the display will look like an inverted impedance measurement.
在电流监控器中，输出到负载的电流将是测量值，并将显示出来。这类似于导纳测量。因此，显示屏看起来就像一个倒置的阻抗测量值。
The Input Calibration settings should be similar to those shown in Figure 6. These parameters are for a current monitor with an output sensitivity of 0.10 volts/amp and a drive voltage of 2.83 volts. The Volts per Ref. Unit should be the reciprocal of the sensitivity.
输入校准设置应类似于图 6 所示。这些参数适用于输出灵敏度为 0.10 伏/安培、驱动电压为 2.83 伏的电流监控器。每参考电压单位的伏特数单位应为灵敏度的倒数。
The Zero dB Ref. Value should be the drive voltage used.
Zero dB Ref.零 dB 参考值应为所用的驱动电压。

Figure 6 - Input calibration settings for using a current monitor
图 6 - 使用电流监控器时的输入校准设置

If, on the other hand, one wires the measurement using the series resistance method the voltage drop across the load will be the quantity measured. The display will be similar to an impedance curve. The Input Calibration settings should be similar to those shown in Figure 7.
另一方面，如果使用串联电阻法进行接线测量，负载上的压降将是测量值。显示与阻抗曲线类似。输入校准设置应类似于图 7 所示。
These parameters are for a $1.0\mathrm{k}\mathrm{\Omega }$$1.0\mathrm{k}\mathrm{\Omega }$1.0kOmega1.0 \mathrm{k} \Omega series resistor and a drive voltage of 1.00 volts. The Volts per Ref. Unit should be the reciprocal of the combined series resistance and output impedance of the driving amplifier. The Zero dB Ref. Value should be the drive voltage used.
这些参数适用于 $1.0\mathrm{k}\mathrm{\Omega }$$1.0\mathrm{k}\mathrm{\Omega }$1.0kOmega1.0 \mathrm{k} \Omega 串联电阻和 1.00 伏的驱动电压。每个参考电压单位的伏特数应是驱动放大器的串联电阻和输出阻抗的倒数。单位应为驱动放大器的串联电阻和输出阻抗的倒数。零 dB Ref.零分贝参考值应为所使用的驱动电压。

Figure 7 - Input calibration settings for using a series resistor
图 7 - 使用串联电阻器的输入校准设置
© 2006 Charles Hughes
© 2006 查尔斯-休斯