DM3068测量端口输出电流大小
- 使用电容放电方法测量DM3068输入电阻以及输入电流
01【DM3068输出电阻】
一、测量背景
昨天我们测试了DM3068这款可编程数字万用表的输入阻抗。 我们知道它有两种测量电压时输入阻抗模式， 一个是10兆欧姆，另外一个是高阻模式， 对应的输入电阻大于10G 欧姆。 我们使用外部的一个1微法的电容来测量万用表的它对应的输入阻抗。 在10兆欧姆的模式下， 我们先给电容充到5伏电压。 然后记录万用表测量电容的电压变化情况。 这是一个标准的RC放电过程。 根据放电数据拟合参数可以知道， 此时数字万用表表输入电阻大约为10兆欧姆。 还是比较准确的。 但另外一种情况令人感到不解， 就是当万用表设置为10G欧姆这种高阻数情况下。 万用表它居然往外输出大约60P安的电流。 注意这个电流在很多情况下已经是非常大了。 为什么会产生这样的一个电流？ 是否所有这种DM3668数字万用表都会输出电流呢？
恰好我手边还有另外一台DM3068数字万用表， 这个万用表是被检修过， 也就是之前它内部出现问题。 平时不使用它，那接下来我们使用相同的方式， 也测量一下它在高阻输入情况下， 它是否也输出大约60PA的电流。 我们使用相同的测量方式来进行对照， 主要是想弄清楚DM3068这款可编程数字万用， 在高阻输入情况下，为什么它会往外输出电流？ 下面我们测试这两台数字万用表高阻状态下， 它对外输出电流的情况。
二、测量结果
首先我们将电路板上的电容通过镊子放电完毕，然后记录万用表， 它在这个过程中所测量的100个数据点耗时大概120秒。 这时候我们设置万用表的输入阻抗的模式为大于10G 欧姆模式。 通过测试数据，我们可以计算出， 在外面一微法的电容上， 根据它的电压变化率，可以知道。 万表，它对外输出大约57.9P安的电流， 这个电流和昨天测试的电流基本上都在一个数量级。
#!/usr/local/bin/python# -*- coding: gbk -*-#============================================================# TEST1.PY -- by Dr. ZhuoQing 2026-09-26## Note:#============================================================fromheadmimport*fromtsmodule.tsvisaimport*dm3068open()tdim=[]vdim=[]C=973e-9starttime=time.time()foriinrange(100):t=time.time()-starttime tdim.append(t)v=dm3068vdc()vdim.append(v)time.sleep(1)tspsave("measure",tdim=tdim,vdim=vdim)printff(i,t,v)dv=vdim[-1]-vdim[0]dt=tdim[-1]-tdim[0]Ioffset=dv*C/dt printff(dv,dt,Ioffset)plt.plot(tdim,vdim,lw=3)plt.xlabel("Time(s)",color="steelblue",fontsize=24)plt.ylabel("Vout(V)",color="steelblue",fontsize=24)plt.grid(True,which='both',linestyle='--',alpha=0.7)plt.tight_layout()plt.show()#------------------------------------------------------------# END OF FILE : TEST1.PY#============================================================tdim=[0.0000,1.4656,2.6597,3.8690,5.0795,6.2949,7.4721,8.7079,9.9193,11.0979,12.3361,13.5448,14.7678,15.9687,17.1496,18.3838,19.5947,20.8048,22.0147,23.1975,24.4320,25.6418,26.8265,28.0596,29.2721,30.4785,31.6892,32.8672,34.1074,35.3203,36.5230,37.7346,38.9232,40.1546,41.3613,42.5448,43.7822,44.9948,46.2033,47.4097,48.5958,49.8321,51.0390,52.2178,53.4570,54.6664,55.8775,57.0883,58.2687,59.5018,60.7177,61.9249,63.1296,64.3212,65.5532,66.7619,67.9440,69.1813,70.3912,71.5998,72.8098,73.9875,75.2259,76.4368,77.6433,78.8552,80.0353,81.2747,82.4814,83.6696,84.9022,86.1111,87.3212,88.5312,89.7120,90.9492,92.1565,93.3437,94.5753,95.7856,96.9928,98.2034,99.3859,100.6234,101.8310,103.0456,104.2529,105.4324,106.6713,107.8797,109.0587,110.3014,111.5064,112.7169,113.9274,115.1094,116.3452,117.5539,118.7622,119.9735]vdim=[0.0099,0.0100,0.0100,0.0101,0.0102,0.0103,0.0103,0.0104,0.0105,0.0106,0.0106,0.0107,0.0108,0.0109,0.0109,0.0110,0.0111,0.0112,0.0112,0.0113,0.0114,0.0114,0.0115,0.0116,0.0117,0.0117,0.0118,0.0119,0.0120,0.0120,0.0121,0.0122,0.0122,0.0123,0.0124,0.0125,0.0125,0.0126,0.0127,0.0128,0.0128,0.0129,0.0130,0.0131,0.0131,0.0132,0.0133,0.0133,0.0134,0.0135,0.0136,0.0136,0.0137,0.0138,0.0138,0.0139,0.0140,0.0141,0.0141,0.0142,0.0143,0.0143,0.0144,0.0145,0.0146,0.0146,0.0147,0.0148,0.0148,0.0149,0.0150,0.0151,0.0151,0.0152,0.0153,0.0153,0.0154,0.0155,0.0156,0.0156,0.0157,0.0158,0.0158,0.0159,0.0160,0.0160,0.0161,0.0162,0.0163,0.0163,0.0164,0.0165,0.0165,0.0166,0.0167,0.0168,0.0168,0.0169,0.0170,0.0170]接下来我们更换第2台DM3068数字万用表进行测试， 这个万用表之前被检修过。 我们同样将它测量电压输入模式设置为高阻状态。 通过记录100个数据点的变化， 我们可以看到电容电压持续上升， 也表示在此状态下它仍然有微弱的电流输出。 根据外部电容电压变化率， 我们可以计算出对应的输入电流为69.3P安， 和刚才第1个测量的万用表相比， 它的输出电流大小增加了大约40%左右。
#!/usr/local/bin/python# -*- coding: gbk -*-#============================================================# TEST1.PY -- by Dr. ZhuoQing 2026-09-26## Note:#============================================================fromheadmimport*fromtsmodule.tsvisaimport*dn3068open(19)tdim=[]vdim=[]C=973e-9starttime=time.time()foriinrange(100):t=time.time()-starttime tdim.append(t)v=dn3068vdc()vdim.append(v)time.sleep(1)tspsave("measure",tdim=tdim,vdim=vdim)printff(i,t,v)dv=vdim[-1]-vdim[0]dt=tdim[-1]-tdim[0]Ioffset=dv*C/dt printff(dv,dt,Ioffset)plt.plot(tdim,vdim,lw=3)plt.xlabel("Time(s)",color="steelblue",fontsize=24)plt.ylabel("Vout(V)",color="steelblue",fontsize=24)plt.grid(True,which='both',linestyle='--',alpha=0.7)plt.tight_layout()plt.show()#------------------------------------------------------------# END OF FILE : TEST1.PY#============================================================tdim=[0.0000,1.4514,2.6611,3.8710,5.0610,6.2899,7.4985,8.7112,9.9190,11.1010,12.3363,13.5457,14.7539,15.9679,17.1533,18.3827,19.5921,20.7810,22.0165,23.2260,24.4337,25.6449,26.8234,28.0595,29.2713,30.4815,31.6878,32.8687,34.1064,35.3192,36.5279,37.7364,38.9148,40.1555,41.3624,42.5503,43.7816,44.9955,46.2013,47.4126,48.5886,49.8273,51.0381,52.2464,53.4557,54.6447,55.8768,57.0834,58.2732,59.5051,60.7135,61.9234,63.1333,64.3168,65.5521,66.7673,67.9743,69.1778,70.3658,71.6052,72.8074,74.0172,75.2304,76.4463,77.6464,78.8568,80.0345,81.2724,82.4822,83.6951,84.9011,86.0789,87.3176,88.5291,89.7377,90.9498,92.1294,93.3670,94.5747,95.7628,96.9936,98.2038,99.4132,100.6230,101.8013,103.0420,104.2533,105.4609,106.6699,107.8578,109.0885,110.2987,111.4765,112.7154,113.9262,115.1348,116.3456,117.5310,118.7621,119.9757]vdim=[0.0055,0.0056,0.0057,0.0058,0.0059,0.0060,0.0060,0.0061,0.0062,0.0063,0.0064,0.0065,0.0066,0.0066,0.0067,0.0068,0.0069,0.0070,0.0071,0.0072,0.0073,0.0073,0.0074,0.0075,0.0076,0.0077,0.0078,0.0079,0.0080,0.0080,0.0081,0.0082,0.0083,0.0084,0.0085,0.0086,0.0087,0.0087,0.0088,0.0089,0.0090,0.0091,0.0092,0.0093,0.0093,0.0094,0.0095,0.0096,0.0097,0.0098,0.0099,0.0099,0.0100,0.0101,0.0102,0.0103,0.0104,0.0105,0.0105,0.0106,0.0107,0.0108,0.0109,0.0110,0.0111,0.0111,0.0112,0.0113,0.0114,0.0115,0.0116,0.0117,0.0117,0.0118,0.0119,0.0120,0.0121,0.0122,0.0123,0.0124,0.0124,0.0125,0.0126,0.0127,0.0128,0.0129,0.0130,0.0130,0.0131,0.0132,0.0133,0.0134,0.0135,0.0136,0.0136,0.0137,0.0138,0.0139,0.0140,0.0141]※总结 ※
本文从重新测试了两款可编程数字万用， 在高阻输入状态下，它的测量端口输出电流的大小， 万用表的型号为DM3068。 当它在测量电压下，输入模式设置为高阻状态， 他对外会持续输出50至70 P安电流， 这个电流会对外部测量电容进行充电。 那么问题来了，腕表在此模式下， 它居然会对外输出电流， 这个电流是如此之高， 那么究竟DM3668。 在这种模式下，它究竟会当做会用作什么测量用途呢？
