霍爾馬克的楊氏模量儀（型號：HO-ED-M-02）用于測量棒材的楊氏模量。楊氏模量是彈性材料的剛度的量度，并且是用于表征材料的量。根據(jù)材料的確切組成，它可能會發(fā)生很大變化。如果光束在其中點受力，則產(chǎn)生的凹陷將不會形成圓弧。這種彎曲稱為非均勻彎曲。如果梁的兩端都加載，則產(chǎn)生的高程將形成一個圓弧。這種彎曲稱為均勻彎曲。在均勻彎曲和不均勻彎曲中，使用兩種方法來測量鋼筋的楊氏模量。它們是銷和顯微鏡法和光學杠桿法。
在非均勻彎曲時，梁（米標尺）對稱地支撐在兩個刀刃上，并在其中心受力。*大凹陷發(fā)生在其中心。由于僅在梁的某個點施加載荷，因此這種彎曲在整個梁中都是不均勻的，因此將梁的彎曲稱為不均勻彎曲。
在均勻彎曲時，將導條對稱地放置在兩個刀刃上。兩個重物吊架懸掛在離刀刃等距離的位置。權(quán)重被一一加起來，并得到相應的讀數(shù)。根據(jù)這些讀數(shù)，確定給定質(zhì)量的鋼筋中點的平均高度（e）。
1. Non uniform bending
Consider a bar of thickness d and breadth b is supported symmetrically between two knife edges at a distance l distance apart and loaded with a weight Mg at the center. The depression at the midpoint is given by,
Z = Mgl3 / 48 Y ( bd3 / 12 )
The Young’s Modulus of the material of the bar
Y = Mg (l3 / z) / 4bd3
For a constant mass M, the quantity l3/z is a constant from which Y can be calculated.
2. Uniform bending
Consider a bar of thickness d and breadth b is supported symmetrically between two knife edges at a distance l distance apart and loaded with equal weights Mg at the ends at equal distance p from each knife edges. The elevation at the midpoint is given by,
Z = Mgpl2 / 8Y (bd3 / 12)
Y = 3 Mgpl2 / 2bd3z
According to the theory of non uniform bending, for a bar of thickness d and breadth b ; supported by two knife edges l distance apart, the depression at the midpoint due to a load M is given by,
Z = Mgl3 / 48 Y (bd3 / 12)
If the optical lever, scale and laser arrangement are used for measuring the depression, the angle of twist of optic lever
Θ = z / x
Where x is the perpendicular distance to the legs of the optical lever
If y to the shift on the scale arranged at a distance D from the laser of the optical lever then
Θ = y / 2D
Z = xy / 2D
Thus,
Y = Mg / 2bd3x (Dl3 / y)
For a mass M, the quantity Dl3/y is a constant.
Y = 3Mg pl2 / 2bd3z
Y = 3Mgpl2 / bd3xy)