Intro

I have wasted so much time while trying to use horrible quality Pomona 3770 some years back. Despite the noticeable prices 3770 posts are machined woth bad tolerances with shavings, steel nuts and very brittle thin plastic. They look cheap, they crack easy and make you do annoying repair and recalibration for the instrument every time they brake. I’ll never use 3770 in any of our projects, but there is very little commercial alternatives were available. Low Thermal manufactured model 2758 binding posts which are very nice quality but price almost tripled over the years and number of production delays made them hard to buy. IET makes BP-1000 high current low-thermal emf posts but they expensive at $69 USD per piece.

But this wasn’t acceptable and eventually metrology enthusiasts came forward to fill the void with TBP series posts. Back in 2018 TBP-1 posts were released and later on different version was also made, such as these beauties for high-resistance applications with unique PTFE insulators.

The latest version called TBP-3 are the 5-way low thermal e.m.f. binding post with D tube and/or light pipe for LED backlight applications. These post were designed and built by volt-nut community enthusiasts to support various metrology projects and designs. Posts were designed and launched some years back but were under lengthy testing procedure for validation.

Approximate prices for small quantity are ~19 USD for pure copper version and about ~20 USD for gold-over-nickel plated copper version. Price drops down a little with larger quantity orders (10 pcs+).

The binding posts are available in gray or black with different color coded inserts. The post is made of tellurium copper, the lock washers and nuts of copper, all with optional nickel/gold plating. The plastic parts are manufactured in low leakage polycarbonate, making them ideal for high-insulation applications, standards and precision test equipment.

Datasheet is also available here.

Models and ordering information

Standard colors are black or gray bodies with black, white, red, blue, or green colored coded inserts. All binding post come with both D tube and light pipe.

Part-number for ordering follows the format : TBP3-A-B-XX. Designators and part list decode is available in table below:

Post model code	A designator, plating	B = insulation color	XX Insert color
TBP3-A-B-XX	0 = CuTe non-plated connector	0 = Black plastic color	00 – Black insert ring
	1 = CuTe + Nickel + Gold plated connector	1 = Milk grey plastic color	01 – White insert ring
			02 – Red insert ring
			03 – Blue insert ring
			04 – Green insert ring

Materials used in TBP3

Insulated thumb nut metal, molded in plastic : CuTe
Insulation material : PC = Polycarbonate
Mounting Base : Polycarbonate
Insulator holder : Polycarbonate
Lock washer : Cu
Hex Nut : M4 thread, Cu
Binding Post body : CuTe

The binding posts can be used with LED backlight. Therefore, three side LED’s are arranged in 120° angle to shine at the light pipe made out of frosted transparent polycarbonate.

Accessories

Additional accessories made of T2 copper, that are compatible with TBP-3 binding posts, are available on request.

Description	Part number
Low thermal e.m.f. fork terminal/spade lug	Spade lug 12-14 T2 Copper
Low thermal e.m.f. fork terminal/spade lug	Spade lug 22-16 T2 Copper
Low thermal e.m.f. ring terminal	O ring tongue 16-22 T2 Copper
Low thermal e.m.f. hex nut	#8-32 T2 Copper Hex Nuts

Photographs

I have also demo PCB module with RGB backlight for these TBP3 low thermal posts. It allows to set various colors for each individual post for appearance review and demonstration.

Features close-up photographs

Gold-over-nickel plated post version:

Pure-copper version for more critical low voltage metrology applications:

Here one of the posts with sanded surfaces to reveal nickel under gold surface as well as example side RGB-backlight placement on mounted PCB.

Happy ordering!