Heat pulse (HP) sensors have been used extensively to measure soil thermal properties and volumetric water content (θ) simultaneously. Probe spacing (R), the distance between heater probe and temperature probe, is routinely calibrated in agar solution before making HP measurements. In reality, R may change due to probe deflection at insertion into soil, causing uncertainties in HP measured volumetric heat capacity (C) and θ. In this paper, we present a simple on‐site calibration method for determining in‐situ R by using theoretical C values estimated from soil bulk density and θ values of intact soil cores collected near the sensor locations at the end of experiment. The proposed approach was tested on two field soils where C and θ were monitored continuously. Inconsistent results were observed between agar‐calibrated R values (R_agar) and R values obtained from in‐situ calibration (R_in‐situ). Maximum difference between R_agar and R_in‐situ reached 20% of R_agar. Compared to TDR measured θ, using R_agar led to root mean square errors (RMSEs) of 0.26 MJ m⁻³ K⁻¹ in C and 0.06 m³ m⁻³ in θ on average. For R_in‐situ, the RMSE of C was less than 0.16 MJ m⁻³ K⁻¹ and RMSE of θ was within 0.04 m³ m⁻³. Thus, the use of in‐situ probe spacing calibration improved the accuracies of HP measured C and θ.

中文翻译：

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原位探头间距校准改进了用于测量土壤热容和水含量的热脉冲方法

热脉冲（HP）传感器已被广泛用于同时测量土壤的热特性和体积水含量（θ）。在进行HP测量之前，通常在琼脂溶液中校准探头间距（R），即加热器探头和温度探头之间的距离。实际上，R可能会由于探头插入土壤时的偏转而发生变化，从而导致HP测量的体积热容（C）和θ不确定。在本文中，我们提出了一种使用理论C确定现场R的简单现场校准方法根据实验结束时传感器位置附近收集的完整土壤芯的土壤容重和θ值估算的值。在连续监测C和θ的两种田间土壤上测试了该方法的有效性。琼脂校准之间观察到不一致的结果[R值（[R_琼脂）和- [R从原位校准获得的值（[R_原位）。之间最大差值ř_琼脂和- [R_原位达20％ř_琼脂。与TDR测量的θ相比，使用R_琼脂导致的均方根误差（RMSE）为0.26 MJ·m^-3 ķ ^-1在Ç和0.06米³米^-3在θ上平均。对于_原位R，C的RMSE小于0.16 MJ m ^-3 K ^-1，θ的RMSE在0.04 m ³ m ^-3内。因此，使用原位探头间距校准可以提高HP测量的C和θ的精度。