熱電偶校準及誤差實驗指導(dǎo)

熱電偶校準及誤差實驗指導(dǎo)一、用途鎳鉻-鎳硅熱電偶是非貴金屬熱電偶中性能最穩(wěn)定的一種，熱電勢較大，且有接近直線的分度曲線，因此使用最廣。熱電偶遇溫度顯示儀表配合，主要用于測量氣體、蒸汽、液體等介質(zhì)的溫度。常用的有是帶保護管套的、裸裝的和鎧裝的幾種。二、主要技術(shù)性能1、正常工作環(huán)境中性或氧化性氣氛。長時間使用溫度0～900℃，短時間使用溫度1000～1200℃。2、分度特性分度號EU-2(由表2-1給出)3、基本誤差三等標準熱電偶：≤±3（℃）工業(yè)通用熱電偶：≤｛±3±0.0075（X-400）｝℃三、工作原理熱電偶是根據(jù)金屬的熱電效應(yīng)設(shè)計制作的。兩種不同的導(dǎo)體組成一個封閉的回路，便構(gòu)成了一個熱電偶，如果熱電偶兩端結(jié)點溫度不同，回路中就會產(chǎn)生熱電勢，這個熱電勢的大小只與構(gòu)成熱電偶的導(dǎo)體成分以及與熱電偶兩端的溫度有關(guān)。但是，應(yīng)該注意，如果熱電偶本身材料不均勻，那么，由于溫度梯度的存在，可能產(chǎn)生附加電勢。鎳鉻-鎳硅熱電偶的正極是鎳鉻合金，成分為鎳89%，鉻10%，鐵1%，負極是鎳硅合金，成分為鎳97%，硅2.5%，錳0.5%。這兩種電極材料的高溫抗氧化能力及抗腐蝕能力都很強，熱電性能穩(wěn)定，但鎳硅材料在高溫下易受還原氣氛的有害影響。四、使用注意事項1、熱電偶裸裝，其電極務(wù)必避免受到機械損傷，而且只能用在中性或氧化性氣氛環(huán)境中；在還原性氣氛中或在腐蝕介質(zhì)環(huán)境中使用，必須有密封良好的保護套管。2、熱電偶要有足夠的插入深度。3、與二次儀表連接使用銅-康銅補償導(dǎo)線，其導(dǎo)線絕緣層著色：正極（銅）為紅色，負極（康銅）為藍色。因補償導(dǎo)線，分度號Eu-2。

表2-1鎳鉻-鎳硅熱電偶分度表（自由端溫度為0℃）工作端溫度（℃）熱電勢(mV)0123456789-50-1.86-1.82-1.79-1.75-1.72-1.68-1.64-1.60-1.57-1.54-40-1.50-1.46-1.43-1.40-1.36-132-1.28-1.25-1.21-1.18-30-1.14-1.10-1.07-1.03-0.99-0.96-0.92-0.88-0.84-0.81-20-0.77-0.74-0.70-0.66-0.62-0.59-0.55-0.51-0.47-0.43-10-0.39-0.35-0.31-0.27-0.23-0.20-0.16-0.12-0.08-0.0400.000.040.080.120.160.200.240.280.320.36100.400.440.480.520.560.600.640.680.230.76200.800.840.880.920.961.001.041.181.121.16301.201.241.281.321.861.411.451.491.531.57401.611.651.691.731.771.821.861.901.941.98502.022.062.102.142.182.232.272.312.352.39602.432.472.512.562.602.642.682.722.772.81702.852.892.932.973.013.063.103.143.183.22803.263.303.343.393.433.473.513.553.603.64903.683.723.763.813.853.893.933.974.024.061004.104.144.184.224.264.314.354.394.434.471104.514.554.594.634.674.724.764.804.844.881204.924.965.005.045.085.135.175.215.255.291305.335.375.405.455.495.535.575.615.655.691405.735.775.815.855.895.985.976.016.056.091506.136.176.216.256.296.336.376.416.456.491606.536.576.616.656.696.736.776.816.856.891706.936.977.017.057.097.137.177.217.257.201807.337.377.417.457.497.537.577.617.657.691907.737.777.817.857.897.937.978.018.058.092008.138.178.218.258.298.338.378.418.458.492108.538.578.618.658.698.738.778.818.858.892208.938.979.019.069.109.149.189.229.269.302309.349.389.429.469.509.549.589.619.669.702409.749.789.829.869.909.959.9910.0310.0710.11

工作端溫度（℃）熱電勢(mV)012345678925010.1510.1910.2310.2710.3110.3510.4010.4410.4810.5226010.5610.6010.6410.6810.7210.7710.8140.8510.8910.9327010.9711.0111.0511.0911.1311.1811.2211.2611.3011.3428011.3811.4211.4611.5111.5511.5911.6311.6711.7211.7629011.8011.8411.8811.9211.9612.0112.0512.0912.1312.1730012.2112.2512.2912.3312.3712.4212.4612.5012.5412.5831012.6212.6612.7012.7512.7912.8312.8712.3112.9613.0032013.0413.0813.1213.1613.2013.2513.2913.3313.3713.4133013.4513.4913.5313.5813.6213.6613.7013.7413.7913.8334013.8713.9113.9514.0014.0414.0814.1614.1614.2114.2535014.3014.3414.3814.4314.4714.5114.5915.5914.6414.6836014.7214.7614.8014.8514.8914.9315.0115.0115.0615.1037015.1415.1815.2215.2715.3115.3515.4315.4315.4815.5238015.5615.6015.6415.6915.7315.7715.8515.8515.9015.9439015.9816.0216.0616.1116.1516.1916.2716.2716.3216.3640016.4016.4416.4916.5316.5716.6216.7016.7016.7416.7941016.8316.8716.9116.9617.0017.0417.1217.1217.1717.2142017.2517.2917.3317.3817.4217.4617.5417.5417.5917.6343017.6717.7117.7517.7917.8417.8817.9617.9618.0118.0544018.0918.1318.1718.2218.2618.3018.3818.3818.4318.4745018.5118.5518.6018.6418.7318.7718.8118.8518.8518.9046018.9419.9819.0319.0719.1619.2019.2419.2819.2819.3347019.3719.4119.4519.5019.5819.6219.6619.7119.7119.7548019.7919.8319.8819.9220.0120.0520.0920.1320.1320.1849020.2220.2620.3120.3520.4420.4820.5220.5620.5620.6150020.6520.6920.7420.7820.8220.8720.9120.9520.9921.0451021.0821.1221.1621.2121.2521.2921.3321.3721.4221.4652021.5021.5421.5921.6321.6721.7521.7621.8021.8421.8953021.9321.9722.0122.0622.1022.1422.1822.2222.2722.3154022.3522.3922.4422.4822.5222.5722.6122.6522.6922.7455022.7822.8222.8722.9122.9123.0023.0423.0823.1223.1756023.2123.2523.2923.3423.3423.4223.4523.5023.5523.5957023.6323.6723.7123.7523.7523.8423.8823.9223.9624.0158024.0524.0924.1424.1824.1824.2724.3124.3524.3924.4459024.4824.5024.5624.6124.6524.6924.7324.7724.8224.86工作端溫度（℃）熱電勢(mV)012345678960024.9024.9424.9925.0325.0725.1225.1525.1925.2325.2761025.3225.3725.4125.4625.5025.5425.5825.6225.6725.7162025.7525.7925.8425.825.9225.9726.0126.0526.0926.1463026.1826.2226.2626.3126.3526.3926.4326.4726.5226.5664026.6026.6426.6926.7326.7726.8226.8626.9026.9426.9965027.0327.0727.1127.1627.2027.2427.2827.3227.3727.4166027.4527.4927.5327.5727.6227.6627.7027.7227.7927.8367027.8727.9127.9528.0028.0428.0828.1228.1628.2128.2568028.2928.3328.3828.4228.4628.5028.5428.5828.6228.6769028.7128.7528.7928.8428.8828.9028.9629.0029.0529.0970029.1329.1729.2129.2629.3029.3429.3829.4229.4729.5171029.5529.5929.6329.6929.7229.7629.8029.8429.8929.9372029.9730.0130.0530.1030.1430.1830.2230.2630.3130.3573030.3930.4330.4730.230.5630.6030.6430.6830.7330.7774030.8130.8530.8930.9330.9731.0231.0631.1031.1431.1875031.2231.2631.3031.3531.3931.4231.4731.5131.5631.6076031.6431.6831.7231.7731.8131.8531.8831.9331.9832.0277032.0632.1032.1432.1832.3332.2632.3032.3432.3832.4278032.4632.5032.5432.5932.6332.6732.7132.7532.8032.8479032.8732.9132.9533.0033.0433.0933.1333.1733.2133.2580033.2933.333.3733.4133.4533.4933.5333.5733.6133.6581033.6933.7333.7733.8133.8533.9033.9433.9834.0234.0682034.1034.1434.1834.2234.2634.3034.3434.3834.4234.4683034.5134.5434.5834.6234.6634.7134.7534.7934.8334.8784034.9134.9534.9935.0335.0735.1135.1635.2035.2435.2885035.322402535.4035.4434.4835.5235.5635.6035.6435.6786035.722407535.8035.8435.8835.9335.9736.0136.0536.0987036.1236.1736.2136.2536.2936.3336.3736.4136.4536.4988036.5236.5736.6136.6536.6936.7336.7736.8136.8536.8989036.9336.9737.0137.0537.0937.1337.2137.2137.2537.2990037.3337.3737.4137.4537.4937.5337.5737.6137.6537.6991037.7337.7737.8137.8537.8937.9337.9738.0138.0538.0992038.1338.1738.2138.2538.2938.3338.3738.4138.4538.4993038.5338.5768.6138.6538.6938.7338.7738.8138.8638.8994038.9338.9739.0139.0539.0939.1339.1639.2039.2439.28工作端溫度（℃）熱電勢(mV)012345678995039.3239.3639.4039.4439.4839.5239.5639.6039.6439.6896039.7239.7639.8039.8338.8339.9139.9439.9840.0240.0697040.1040.1440.1840.2240.2240.3040.3340.3740.4140.4598040.4940.5340.5740.6140.6140.6940.7240.7640.8040.8499040.8840.9240.9641.0041.0441.0841.1141.1541.1941.23100041.2741.3141.3541.3941.4341.4741.5041.5441.5841.62101041.6641.7041.7441.7741.8141.8541.8941.9341.9642.00102041.0442.0842.1242.1642.2042.2442.2742.3142.3542.39103042.4342.4742.5142.5542.5942.6342.6642.7042.7442.78104042.8342.8742.9042.9342.9743.0143.0543.0943.1343.17105043.2143.2543.2943.3243.3543.3943.4343.4743.5143.55106043.5943.6343.6743.6943.7343.7743.8143.8543.8943.93107043.9744.0144.0544.0844.11441544.1944.2244.2644.30108044.3444.3844.4244.4544.4944.5344.5744.6144.6444.68109044.7244.7644.8044.8344.8744.9144.9544.9945.0245.06110045.1045.1445.1845.2145.2545.2945.3345.3745.4045.44111045.4845.5245.5545.5945.8345.6745.7045.7445.7845.81112045.8545.8945.9345.9646.0046.0446.0846.1246.1546.19113046.2346.2746.3046.3446.3846.4246.4546.7946.3346.56114046.6046.6446.6746.7146.7546.7946.8246.8646.9046.93115046.9747.0147.0447.0847.1247.1647.1947.2347.2747.30116047.3447.3847.4147.4547.4947.5347.5647.6047.6447.67117047.7147.7547.7847.847.8647.9047.9347.9748.0148.04118048.0848.1248.1548.1948.2238.2648.3048.3348.3748.40119048.4448.4848.5148.5548.5948.6348.6648.7048.7448.77120048.8148.8548.8848.9248.9548.9949.0349.0649.1049.13121049.1749.2149.2449.2849.3149.3549.3949.4249.4649.49122049.5349.5749.6049.6449.6749.7149.7549.7849.8249.8123049.8949.8349.9650.0050.0350.0750.1150.1450.1850.21124050.2550.2950.3250.3650.3950.4350.4750.5050.5450.59125050.6150.6550.6850.7250.7550.7950.8350.8650.9050.93126050.9351.0051.0351.0751.1051.1451.1851.2151.2551.28127051.3251.3551.3951.4351.4651.5051.5451.5751.6151.64128051.6751.7151.7451.7851.8151.8551.8851.9251.9551.99129052.0252.0652.0952.1352.1652.2052.3352.2752.3052.33130052.37實驗2-1熱電偶的校驗（熱電偶靜態(tài)特性的測試）之一熱電偶通常工作在高溫環(huán)境中，受氣氛影響，長期使用，其熱電特性可能發(fā)生變化，因而，有必要進行熱電偶檢查和校驗。熱電偶校驗之前首先是外觀檢查，即察看熱電偶導(dǎo)線表面是否清潔，色澤均勻，無色斑；接點焊合牢固，表面光滑，無氣孔，必要時需清洗或重新焊合。熱電偶的校驗是要確定熱電的電勢與溫度的對應(yīng)關(guān)系。熱電偶的校驗常用比較法即被檢熱電偶與標準熱電偶的熱端保持在同一溫度，它們的冷端都恒定在冰點。如此，測量標準熱電偶的熱電勢可得到其熱端溫度的測量值，這個測量值對于被檢熱電偶來說則是其熱端溫度下的實際值T。同時，由被檢熱電偶得到其熱端溫度下的測量值X。于是，被檢熱電偶的修正值C＝T-X。對工業(yè)用鎳鉻-鎳硅熱電偶的校驗，標準熱電偶通常用三級標準熱電偶。檢定點溫度一般是400、600、800℃。電爐在給定溫度保溫直到標準熱電偶的熱電勢穩(wěn)定后開始測量，標準熱電偶所示溫度與檢定點的偏差應(yīng)不大于5℃。本實驗要求：1、用三級標準鎳鉻-鎳硅熱電偶校驗普通鎳鉻-鎳硅熱電偶，給出檢定點（800℃）溫度的修正值，并估計被檢熱電偶的基本誤差。2、通過該實驗，要求掌握熱電偶校驗方法，并對熱電偶的基本誤差有所認識，同時掌握標準熱電偶電位差計的使用方法。實驗報告（范例）熱電偶的校驗一、實驗?zāi)康?、校驗一支鎳鉻-鎳硅熱電偶（檢定點溫度800℃）2、掌握標準電位差計的使用及熱電偶的校驗方法，確定被檢熱電偶的基本誤差。二、實驗原理熱電偶的校驗是要確定熱電偶的電勢與溫度的對應(yīng)關(guān)系。熱電偶的校驗常用比較法，即被檢熱電偶與標準熱電偶的熱端保持在同一溫度，它們的冷端都恒定在冰點，如此，測量標準熱電偶的熱電勢可得到其熱端溫度的測量值，這個測量值對于被檢熱電偶來說則是其熱端溫度下的實際值T。同時，由被檢熱電偶得到其熱端溫度下的測量值X。于是，被檢熱電偶的修正值C＝T-X。三、實驗儀器與裝置1、標準熱電偶：三級標準鎳鉻-鎳硅熱電偶，分度號EU-2修正值：C400＝-0.03Mv（-0.8℃）C600＝-0.04Mv（-1.0℃）C800＝-0.05Mv（-1.3℃）2、被檢熱電偶：鎳鉻-鎳硅熱電偶，分度號EU-2基本誤差<{±3±0.0075（X-400）}℃3、標準直流電位差計：UJ-36型4、管式爐，爐膛內(nèi)安放一塊不銹鋼制的均熱筒，管式爐用精密溫度控制儀控溫。5、冰瓶，瓶內(nèi)充滿了冰屑與水的混合物。上述儀器組成熱電偶校驗裝值，如圖2-1所示，被檢熱電偶①與標準熱電偶④一起放在管式電爐③爐膛中的均熱筒②的空腔內(nèi)，它們的冷端同置于冰瓶⑤內(nèi)，用銅導(dǎo)線⑧通過轉(zhuǎn)換開關(guān)⑦與UJ-36型電位差計⑥相連接。圖2-1熱電偶校驗裝置四、實驗步驟1、外觀檢查熱電偶導(dǎo)線表面清潔，色澤均勻，無色斑；接點焊合牢固，表面光滑，無氣孔。2、檢查管式爐實驗裝置管式爐自動控溫，檢查整套裝置是否完備；爐膛高溫區(qū)放置有金屬均熱筒，其空腔深度直徑比大于10。3、安放熱電偶及按圖接線被檢熱電偶與標準熱電偶都應(yīng)套上絕緣管，熱端并排，且用細電阻絲將他們捆成一束。把該熱電偶束插入管式電爐中的金屬均熱筒的空腔內(nèi)，插到底，再退出2～3毫米，然后，用耐火纖維將管式爐口堵住，熱電偶從耐火纖維中通過。熱電偶的冷端與銅導(dǎo)線連接，同樣套上絕緣管，且用細電阻絲將它們捆成一束，置于冰瓶內(nèi)的玻璃管中，插到底，再用棉花將玻璃管口堵住，熱電偶從中通過，熱電偶的冷端與銅導(dǎo)線連接，銅導(dǎo)線通過轉(zhuǎn)換開關(guān)與UJ-36型電位差計相連接。察看冰